This is when a character with mental problems, and often some physical deformity, is locked away because s/he will never fit into society, usually either in the attic or in the basement, and often by a Corrupt Hick. The more of a Big Fancy House, the better; in fact, the smarter ones will sometimes have a secret system of peepholes and secret passages so they can move around as they please. They also tend to be inbred.
There are two basic plotlines for this type of character:
The protagonist is an outsider, wondering what kind of bizarre secret the Corrupt Hicks are keeping. The Bertha will then either tend to be Dragon-type enemies with little personality of their own, or they're The Grotesque, sympathetic victims. When done well, this can be an effective scare because it so aptly encapsulates the frightening insularity of the Town with a Dark Secret.
The main characters have just moved into a new house, and unbeknownst to them, are being watched by one of these whose caretakers have died some time ago. These are scary because of how they personify the fears of buying a new house: that your house has some hideous aspect that you haven't seen, but can see you.
This trope is named for the landmark work of feminist literary criticism by Sandra Gilbert and Susan Gubar, referring to Mr. Rochester's wife in Charlotte Brontë's Jane Eyre. The analysis indicates that this trope first popularly appeared, in all places, in Victorian women's literature, where depicting some women as crazy people was an easy way to make female villains with whom readers would be unlikely to sympathize. Obviously, this plan was not a complete success.
Subversions occasionally arise when it turns out that there was a very good reason this person was locked away in the first place. Maybe they're Axe Crazy, maybe they suffer from an extremely contagious form of illness, or perhaps the person is being hidden for their own safety to keep them from being kidnapped or murdered.
Usually either Ax-Crazy or The Grotesque. Compare Man in the Iron Mask.
Not to be confused with the company involved with the first season of Smash. Or the episode of The Sarah Jane Adventures which also borrows its name from the book (but isn't an example).
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Sakurako from Sakura Gari, who has been locked in an old house for nine years. We later find out more about her. She had always been The Unfavorite even before Souma arrived to the family, but was allowed to live in the more modern Big Fancy House. Even after Lady Saiki's death, she was staying there - it was only after her Creepy Child behavior went Up to Elevenin public that she was confined to the old house as punishment, with the butler Katou as her personal caretaker. The rest of the family and servants tell the outsiders that Sakurako died of illness a year after her mom died. Also, unlike other cases Sakurako is allowed to leave the "attic" and come back to the main home, mostly because of a fire; when speaking to Souma, she also offhandedly mentions that she still has difficulty to walk due to being locked in a relatively small space for so long.
Hisoka Kurosaki from Yami No Matsuei is locked away by his parents because of his empathic powers. In the manga, it's also to keep him from being the prey to a demon who raped both of his parents and forcibly impregnated his mom.
At least two cases from Detective Conan have people trapped in attics and becoming unstable.
One featured a gifted writer, hiding in the attic after committing a murder over a decade ago. He was very sane indeed, just rather confused/fascinated over a cellphone.
One case had a subversion. Ran's father is called in by two men, to find treasure allegedly hidden in their new house. Throughout the story, Conan catches glimpses of a shadowy, scary figure sneaking around, leading readers to suspect this trope. It turns out that the figure is not dangerous or insane, but was the actual owner of the house, locked in the attic when the two men broke in to steal the treasure. She's fine when she's released.
As a result of her insanity caused by the events of the Eclipse, Casca from Berserk is locked in an elf mine for two years for her own safety, since the elf mine is protected from the evil spirits that are attracted to Casca's brand.
One of Sabretooth'spossible backstories shows him as a child chained up in the basement with a dog dish, his father periodically coming down to yank out his claws and teeth.
The mini-series Freaks Of The Heartland is told from the perspective of the normal brother of one of the several Grotesques who've been locked away since the small town's Bizarre Baby Boom years ago.
At one point, Dv8, Gen13's Evil Counterpart, meets an even eviller team called Twist. One of Twist's Kick the Dog moments is when one of them shows Dv8's Evo a cellar under their base crammed full of Body Horrors mutated by the same Phlebotinum that gave the others powers, and tries to get him to have sex with her in front of them.
Horridus from The Savage Dragon and Freak Force is a reptilian-looking Half-Human Hybrid whose parents kept her chained up in the basement. But TSD being a comic book where the main hero is a green guy with a fin on his head, Horridus didn't have that much trouble integrating with society.
The Jersey Devil in Hoax Hunters was born a hideous monster, and grew up in the basement of a New Jersey orphanage. Two windows were built into the building just for him, covered with chicken wire, so he could see the sun and get fresh air.
Karl Childers in Sling Blade spends his childhood as one of these. The long-term hospitalization following his murder of his mother may also qualify.
Sloth from The Goonies. A sympathetic example of Type 1.
The title creatures of The People Under the Stairs. Tweaked, however, in that the imprisoned things weren't born that way, but were kidnapped as young children and imprisoned under horrid conditions that caused their degeneration.
The freak in the title of Castle Freak has been locked in a dungeon by his mother since his early childhood, fed scraps and beaten regularly, among other things. When she dies he is forced to break out or starve. As you'd expect he's not all there. Definitely qualifies as a Grotesque.
The first Basket Case film, although Belial's titular "attic" is portable and he doesn't seem to complain about staying hidden. Furthermore he's even said to prefer to keep to himself in the sequels.
If mobile "attics" count, then Blaster from Mad Max: Beyond Thunderdome might be a borderline case. He lives behind an armored mask and never associates with anyone except as Master's transport, and when the mask comes off, it's revealed that he has Down's Syndrome and is incapable of surviving in Bartertown's cutthroat society without the protective Master's supervision.
The Orphanage does this with the disfigured (but not disabled) Tomas by putting him in a mask and keeping him in a secret room. But in something of a subversion he's still allowed out, and to play with other children. The whole matter of keeping him in that room seemed to be a quirk of his overprotective mother, more than anything else.
There's a movie called The Gay Bed and Breakfast of Terror. The crazy Jesus freak mother is keeping her mutant son Manfred (who was conceived during a gang bang at the Republican National Convention) locked up in the attic until she wants him to kill someone.
Invoked in Paranoiac, where Simon thinks he's keeping his brother locked up inside the garage. What he hasn't realized is that Tony is long dead.
In the Hammer HorrorThe Brides of Dracula, Baron Meinster is introduced this way: his mother keeps his locked up in a wing of the castle. Her stated reason is that he is unwell. He tricks the heroine into freeing him on the pretense his mother was trying to cheat him out of his inheritance. It turns out that he's a vampire (the clue is in the movie title) and she was trying to keep him locked up, but didn't have the heart to kill him. Luckily, Peter Cushing shows up and makes everything better.
Saul Femm from The Old Dark House (1932), though not incredibly deformed, is a raging madman with a taste for arson and is thus kept locked in his room by the rest of the family with the help of a mute and deformed butler.
In the Black Christmas (2006) remake, after murdering his father, Billy's mother and her lover keep Billy locked in the attic and use him for sex. He goes steadily more insane before finally snapping one Christmas and murdering them (as well as mutilating his sister/daughter Agnes).
The Penguin in Batman Returns spends his early years as this, before his parents get rid of him by throwing him to the river.
The opening narration for Kiss The Girls describes a self-inflicted version of this: Casanova moves into the attic of the house where his "first love" lives.
Larry Blamire's Dark and Stormy Night has Thessaly, Sinas Cavendar's insane Violent Glaswegian daughter. She's actually treated pretty sympathetically, and is mostly a parody of the Old Dark House example above.
Ronald in Bad Ronald. His mother was sheltering him inside the walls after he'd committed a crime and needed a place to hide, but then she dies and the house is sold, with nobody knowing there's a crazy recluse still living in there.
Invoked, along with many other tropes of Gothic Horror, in The Brood, where a police detective suggests that the childlike mutant that murders the hero's mother-in-law may have been her own deformed child that she was keeping locked in the attic. Likewise, the extreme seclusion in which Oliver Reed's psychiatrist character keeps his patients has aspects of this, especially as the treatment makes them start to physically externalize their emotional problems. Which is exactly where the killers are coming from.
Arthur "Boo" Radley from To Kill a Mockingbird. He only rarely goes out at night, and as a result is so pale that the fearful townsfolk think he's an Evil Albino. He turns out to be utterly harmless and kind.
In the short story, "The Ones Who Walk Away from Omelas" by Ursula K. Le Guin, a filthy, malnourished little child of indeterminate gender is locked in a windowless room and treated as an animal for the vague good of the community.
Mr. Edward Rochester keeps his violently insane wife Bertha locked in the attic of Thornfield in Jane Eyre. Arguably, she was better off there than in what passed for a mental health facility in those days.
Jean Rhys' Wide Sargasso Sea examines this example (yes, this one — same woman) more deeply, giving a possible Back Story of (the literal) Mad Woman in the Attic. It's also a deconstruction, similar in that to "The Yellow Wallpaper", since it's quite clear in this version that her identity was robbed ("Bertha" is not even her real name) and insanity was a role that was forced upon her in an effort of controlling her rather than something that would have happened anyway.
"The Yellow Wallpaper": the main character is bedridden with some illness, and locked up in a room with ugly, confusing wallpaper. She goes crazy as a result. It's primarily a critique on the medicine of the time and the then-disturbingly common practice of keeping "ill" women stuck in a small room with nothing to stimulate them (known as the "Rest Cure", which was actually done to the author and she nearly went insane as a result). It's also a very creepy little psychological horror story.
H.P. Lovecraft was fond of this one: he contributed multiple examples.
The title character of "The Outsider", who is also locked in an Ontological Mystery. It's not clear who's locked him away, though, so it's not sure he fits exactly.
"The Shadow Over Innsmouth": The narrator makes reference to a relative (who has been slowly transforming into a fish man) locked away in an asylum. It's also noted that a few of the Innsmouth people have gotten so deformed that they don't go outside anymore. In this case, it's not that most of the locals would be freaked out by them, since most of them are in on the weird cult, but there's the occasional person around who isn't.
The Gardner family in "The Colour Out of Space" have Nabby Gardner, Nahum Gardner's wife, who goes crazy as a result of exposure to the Colour, and is locked in the attic, where she becomes even more strange... Same thing also happened with Thaddeus, one of the sons.
Rhoby Harris in "The Shunned House". After the presence haunting the house attacks her, her protests are dismissed as just another symptom of her insanity.
In Richard Matheson's short story "Born of Man and Woman", a deformed child is kept chained in the basement by its parents. From the fragmentary descriptions we get, "deformed" is a severe understatement: I will screech and laugh loud. I will run on the walls. Last I will hang head down by all my legs and laugh and drip green [from earlier context, this appears to mean "bleed"] all over until they are sorry they didn't be nice to me.
In the Doctor WhoEighth Doctor Adventures novel Vanishing Point, this trope is reconstructed with a woman keeping a number of deformed and disabled people away from society. But in a bit of a twist, she's quite nice to them, treating them almost like family, and refers to them affectionately as "mooncalves". The story takes place in a Dystopia where they wouldn't be safe anywhere else.
In The Shuttered Room, a woman returns to her childhood home where her insane sister has been imprisoned by an elderly aunt.
The novel Flowers in the Attic is written from the point of view of children locked away in this manner, to hide their existence from their grandfather, who would disinherit their mother (his daughter) for having married and had children by his son by his stepmother, a marriage that resulted in four healthy if somewhat inbred children. The grandmother is very much in on this (delivers meals, etc.), is rather abusive, and as Mom decides she has better things to do with her time than spend it with the kids, becomes the primary outside contact the kids have.
There is a book, Woman in the Wall, where an exceptionally shy girl with a phobia of wide-open spaces did this to herself, choosing to live inside the walls of her house instead of starting school. Then her family stopped seeing her or hearing her talk, though she would eat at night and fix things and sew.
In Frances Hodgson Burnett's The Secret Garden, Mary's uncle keeps his son and Mary's cousin, a bedridden hunchback and sickly child named Colin, hidden away in the house for fear that he will not be able to survive in normal society, and shuns him because of the boy's resemblance to his dead mother.
The creature in Still Life with Crows is one of these kept in a cave who found his way out. Also Subverted in that he started out as a normal child (and apparently a very intelligent one) who was twisted by being forced to live in the cave (his mother gave birth out of wedlock, and her father forced this whole thing on her).
Happens thrice in Harry Potter- to Harry himself in the first book, Barty Crouch Junior, and Dumbledore's little sister Ariana. Subverted with Harry, though, as he was locked in a cupboard under a stairway, but was allowed outside unless he showed signs of magic. He was then freed when all the letters came from Hogwarts, but only because his aunt and uncle thought the letters would stop coming if he slept in a different part of the house. And then he got locked in there anyway, and food was passed to him through a cat flap.
Barty Crouch Junior is a case of Parental Abandonment gone horribly wrong. His father was too busy persecuting and growing in political power on the Dark Witch Hunts to take his son on fishing trips (or even talk to the kid), and the Death Eaters saw one hell of an opportunity to hire the son of the head of the secret police as a mole. When Kakaroff sold him out, Senior sentenced his own son to jail (note that this is a magical jail that is not inspected by ANYONE, so it's a living hell), but was talked out of it by his wife. BC Junior spent the rest of his jail time in the attic of their house... until Voldemort broke him out. He proceeds to bring about the apocalypse in book four.
As for Ariana this was played semi-straight. She went mad after an attack by a gang of Muggle boys, which could be read as rape and was locked up after her father was sent to prison for attacking the Muggle boys, and refusing to say why he did it. Everybody outside the family (the ones who knew about her existence, anyway) figured her mother had locked her up for being a Squib (a wizard with no magical ability), which was a bad thing to be during Ariana's lifetime. Which, in the present in the novels, is still a bad thing; she's indirectly responsible for Russia's secret magician corps (they killed Russian civilians during world war II), as her extremely flashy death provides the muse of the magic corps' leader.
On a lighter note, there is also the ghoul in the Weasleys' attic, although he's treated like a pet, and it's ambiguous exactly what a ghoul is in this world.
Chance the Gardener in Being There was isolated to the Old Man's house all of his life due to his mental retardation and no one but the maids who worked in the house knew he existed. And it's possible he's the Old Man's illegitimate son to boot. The story gets underway once the Old Man dies and he is turned out of the house by the lawyers who came to close the estate. He's a nice, well-spoken person, however (partially due to his being allowed to watch television, giving him some idea of proper behavior and speech), and winds up becoming a Parody Sue when he encounters people who have no idea what he really is.
The novel The Cellar is about a woman who keeps horrific rat-men in her old house.
Paul Auster's City of Glass features a character that was brought up at home in complete isolation as part of a crackpot linguistic experiment by his father. At the time of the story, he has been recovered and mostly rehabilitated - he has learned to speak - but is still quite disconcerting.
Subverted by The Adventure of the Paradol Chamber, a Sherlock Holmes pastiche written by June Thomson. A woman who has befriended a young nobleman hires Holmes to investigate because she's afraid that his servants have imprisoned him in his own house. As it turns out, not only do the servants have a very good reason for locking him up, the nobleman actually wanted to be imprisoned in the first place, since it's revealed that he suffers from a form of hereditary madness that makes him Axe Crazy whenever it strikes. In one of his moments of sanity, the nobleman decided to have himself locked up to keep from being a danger to anyone.
Another subversion comes from The Adventure of the Blanched Soldier, written by Sir Arthur Conan Doyle himself, that is much along these same lines. A soldier who made friends with another younger soldier in the Boer War hires Holmes when he thinks the younger soldier's parents are keeping him imprisoned on their family estate. It turns out that the younger soldier actually contracted what he thinks is leprosy during his time in South Africa, and the family was actually keeping him at home in secret to treat him without his being locked up in a hospital. The younger soldier, who's actually only suffering from treatable icthyosis, voluntarily went along with this.
Then there's "The Yellow Face," in which the suspected Madwoman in the Attic in fact turns out to be simply the main character's mixed-race daughter from a previous marriage, whom she'd kept hidden from her new husband. The story has a happy ending - the little girl is somehow quite healthy and happy, and her new stepfather accepts her immediately, but leaves you kind of unsure if this has lots of Unfortunate Implications or is simply a plea for tolerance at a time when having a mixed-race child was that severe a social liability. Or both.
The protagonist in Neil Gaiman's short story "Forbidden Brides of the Faceless Slaves in the Nameless House of the Night of Dread Desire" has an Aunt Agatha chained in his attic. This has no bearing on the plot, it's just one of the things that establish that he lives in a world of Gothic/adventure/fantasy/horror fiction clichés. A character in the story he's writing is also mentioned to have (had) a "hopelessly insane" wife whom he claimed to be dead. Well, he is writing a realistic, slice of life story based on the world he's living in.
The horror novel Others has a whole wing of a nursing home filled with Freaks in the Attic. Some of them are nice people who just have a physical deformity of varying severity. The Others, though, either because of their imprisonment, or what the director of the home has been doing to them, or just madness, are true monsters.
Both Charlie Angelfield and his father, George, in The Thirteenth Tale go mad after the death of their loved ones, and enter into a sort of self inflicted imprisonment where they lock themselves in their rooms for extended periods of time.
Hortensia from Isabel Allende's "Cuentos de Eva Luna" (Takes of Eva Luna).
In Aunt Dimity: Vampire Hunter, Lori's working hypothesis explaining the creepy looking vampire the twins saw in the woods turns on this idea; she thinks the neighbouring DuCaral family had a crazy son they kept in the house rather than an asylum, and the man escaped (possibly more than once) and stood in the woods watching the boys.
Kind of featured in the Woodland Mystery The Mystery of the Dark Old House, but the guy living in the title house is actually nice, just afraid of the outside world.
The most terrifying kind shows up in the Stephen King short story "Gramma," from Skeleton Crew. She's been senile and dying in the back room for years, and her grandkids are terrified of her...with good reason.
A major theme in What's Bred in the Bone by Robertson Davies is the characters' relations with "the Looner", the young protagonist's mentally defective and physically deformed elder brother who is kept locked in the attic due to the embarrassment at his existence arising from the combination of his developmental deficiencies and his illegitimate conception.
George Cranleigh in the Doctor Who serial "Black Orchid".
Control and Redvers Fenn-Cooper from another Doctor Who story, "Ghost Light".
Also showed up in the NewWho episode "The Idiot's Lantern," in which a family keeps Grandma locked in her bedroom to hide the fact that her mind and face (yes, her face) have been stolen by an alien menace. Note that this episode was written by the same man who played the above David Tattsyrup.
The Doctor in the episode "The Crimson Horror"
Played with in The Twilight Zone episode "The Howling Man". The title character is locked in a monastery cell and spends a lot of time howling mournfully. The protagonist of the story thinks he's crazy, but after the protagonist releases him he turns out to be Satan in disguise. Oops.
Episode called "Home" that dealt with several backwoods-horror tropes, including this one. The local police force with Mulder and Scully's help conclude there must be a woman kidnapped and held by a family of young men who is probably responsible for the murder of a deformed baby. It turns out there is a living woman in the house — she was just assumed to be dead by locals.
"Post Modern Promehtheus", which was a deliberate deconstruction and Affectionate Parody of Frankenstein/deformed monster. Several people have seen him, they just didn't know who he was. He lives with an aging farmer whom he considers his adoptive father. He wanted to protect him by hiding him.
The Babylon 5 episode "Grey 17 is Missing" featured a bizarre cult that had taken over one of the decks of Babylon 5, hidden it on the blueprints and computer schematics, isolated it so no one else could enter... and then locked up themselves on that level with a ravenous alien monster which would periodically eat one of the cult members and thus make them one with the universe via a perfect death.
The MacGyver episode "The Secret of Parker House" had one of these. He turned out to be a nice guy.
Supernatural has this as the twist in "Family Remains", when they discover the last owner of the house kept the twins he conceived with his daughter. The daughter committed suicide and the father was killed by the children, then a new family moved in... Which, par for the course, was played quite disturbingly.
Smallville has some parents lock their boy in the basement and never let him see the sun, because sunlight turns him into a super-strong, violent, rampaging monster.
Done with the half-breed Scorpius in Farscape. The episode "Incubator" reveals that was raised on a Scarran ship in a single room and his only visitor was his "nanny," Tauza- until Scorpius escaped. Quite worryingly, it's implied that Scorpius' mother was imprisoned in the same cell in a pretty similar fashion; according to Tauza, her impregnation at the hands of one of the guards drove her insane- making her a quite literal case of Madwoman In The Attic.
Subverted in one episode of Sanctuary, the one with the young autistic boy who draws monsters, a missing twin brother, their dead father, and the room under the floor, which has shackles welded to one wall. The team originally assume the twin brother was kept down there by an abusive father. By the end of the episode, it turns out that the father was an Abnormal who developed laser eyes during fits, and he was locking himself down there to protect his family.
CSI: Crime Scene Investigation had a rather sweet young woman who happened to have a serious case of hypertrichosis and lived in a secret room in her brother's (also a sufferer, but to a lesser extent) house. She wasn't locked up, but she'd been kept in the house in daylight hours for many years and always retreated to her room when visitors came, so no one knew she was there until after her brother's murder.
In the Made-for-TV MovieBad Ronald, young Ronald's mother locks him up and hides him so the police can't arrest him for a murder he committed. When she dies, he remains in the house, and a new family moves in.
On American Horror Story: Murder House, Constance kept her disfigured son, Beauregard, in the attic. CPS was going to take him away but she had Larry kill him first, claiming he died on natural causes.
On American Horror Story: Freak Show, conjoined twins Dot and Bette Tattler are kept in their house and not allowed to leave; many of the neighbors think that their mother lives alone.
A storyline on All My Children revealed that mysterious millionaire Dimitri Marick (who at the time was a new character) had hidden his wife away, although she wasn't "mad", just severely physically and mentally injured due to a catastrophic riding accident. Making the Jane Eyre ripoff complete, this is all revealed during a ball being held to celebrate Dimitri's engagement to another woman when the wheelchair-bound wife is brought into the ballroom by her mother.Aside from being stunned to learn that her intended is already married, she's further creeped out upon seeing that she bears a strong resemblance to the woman.
Even earlier, this is how Adam's initially evil twin Stuart was introduced, having been locked away by Adam to keep him from harming himself or anyone else.
Reign has one of these in the character of Clarissa, the secret daughter of Catherine, whose face is always hidden in a burlap bag with eyeholes, ever since she was disfigured as a child by a botched attempt at surgery to remove the birthmark that would identify her real father and incriminate the queen. She lurks in the secret passageways of the castle and at times intervenes directly in the political intrigue and action, while taking care to avoid being seen. She is known as "the Ghost." Her lifetime of isolation and abuse results in her becoming an actual madwoman.
The Alice Cooper song "Former Lee Warmer" is sung from the perspective of a man who keeps his mute and apparently insane brother locked up in his attic.
Aphex Twin's Rubber Johnny video features a deformed wheelchair-bound kid in a dark basement.
Crimson Glory's Lost Reflection tells of some poor soul going insane from being trapped in an attic, his only company a reflection in a dusty mirror.
Myth and Legend
If not the Ur Example, then certainly the Knossos Example would be the Minotaur. When Minos decided to keep a bull he had been sent by Poseidon to sacrifice to him, Poseidon made Minos's queen fall in love with the bull and conceive a child with it. To hide the resulting hybrid monster, the king commissioned Daedalus [Icarus' papa, and the man who helped the queen consummate her unnatural love] to build an elaborate labyrinth under the city from which no one could escape.
The Monster of Glamis, a deformed child supposedly born to the Bowes-Lyon family and bricked up in Glamis Castle.
Some versions of the Jersey Devil's Back Story would qualify, depending on how soon after its birth the creature escapes into the woods.
Emo Philips: When I was a kid my parents used to tell me, "Emo, don't go near the cellar door!" One day when they were away, I went up to the cellar door. And I pushed it and walked through and saw strange, wonderful things, things I had never seen before, like... trees. Grass. Flowers. The sun...
In the third edition Ravenloft products from Arthaus, the role of half-orcs is instead given to 'calibans': a PC Race in the Attic, usually born to human mothers who'd been exposed to black magic or curses while pregnant.
Saul Whateley, resident of Gomorra in Deadlands: The Weird West, was locked in the attic by his Big Screwed-Up Family. His insane rantings are still loud enough to keep others in town awake at night. He's useless in a fight, though he might be seen as a sympathetic villain. He actually sees the future, and it's driven him quite mad. The family keeps him alive for scrying... and for unnerving the townsfolk.
GenestealerHybrids in Warhammer 40,000 tend to possess obvious physical deformities such as greyish skin or multiple limbs until the third or fourth generation, and as such have to be hidden from the rest of society, either by their doting parents or the other members of the GenestealerCult. A favored haunt is a hive city's Underhive, the derelict, lawless lower levels of the Imperium's arcologies.
Ogre Gorgers from Warhammer are cast out of a society of Big Eaters for the crime of being born too scrawny. Thrown into the labyrinthine, Warpstone-laced tunnels beneath an ogre settlement, if the Gorger survives the isolation and Warpstone will quickly mutate it into an insane, pallid, degenerate, and above all else ravenous monster.
If you know about Lovecraft's story the game is based on, it's clear that the "woman" had never been a human being. The Third Oath of Dagon demands a follower to marry a pureblooded Deep One, and conceive a child with it. It's less than clear why she would murder her own child though, alien monster or not.
She might have been crazy even by Deep One standards.
It's explained in the tabletop campaign that Dark Corners is based off of: Since the Deep Ones are immortal, the females try to kill all the young, while the males want them to expand the civilization.
The Touhou's uberpoweredlittlevampire, Flandre Scarlet, has lived in the basement of the Scarlet Devil Mansion for the past 495 years at her (slightly) older sister Remilia's behest. Since Flandre has a child's naivety, emotional instability that borders on insanity, and happens to have the power to almost effortlessly destroy anything ("I went 'kyu' and it went boom"), this is probably more of a safety measure than anything else, and official sources suggest that Flandre is okay with the arrangement. Fan portrayals play the situation for horror or drama as needed, and can vary from a sympathetic Flandre being locked away by her domineering older sister to a secretly-heartbroken Remilia forced to cage a psychotically destructive Flan for her (and/or the world's) own good.
Kinzo Ushiromiya in Umineko no Naku Koro ni locked himself in his little mini-apartment at the top of his mansion in Rokkenjima and refuses to come out. He's certainly crazy enough to qualify.
In a subversion, it's not that he's crazy. He's actually, well, dead. Krauss and Natsuhi found his corpse, burned it, and then told the others he was cooping himself there so they wouldn't find out. He probably was that crazy in the last years of his life, though.
Somewhat reversed in Fallout 3: Point Lookout with Kenny, who ran away after his deformed parents hid him in their basement for lacking the right "marks." Judging from most of the inhabitants of the area, what lacking the "marks" means is that he doesn't look like an inbred hillbilly from a rather hamfisted cartoon version of Deliverance.
Double Switch: It is revealed in the game that Eddie was locked in the apartment building basement by his own father, Lyle. Lyle did this because Eddie is Ax-Crazy, and he was just trying to protect people from Eddie.
In Resident Evil: Code: Veronica, a monster codenamed Nosferatu, who is actually the mutated Alexander Ashford, is imprisoned in the Antarctic Base, and escapes shortly after Claire and Steve arrive. In the remake of Resident Evil, the grotesquely deformed and chained Lisa Trevor wanders the basement and backwoods of the Spencer estate.
CloudcuckoolanderBonus Boss Sucre/Sugar from OFF certainly invokes this, being found hanging out in the basement of Zone 0 surrounded by piles of sugar (which doesn't seem too bad unless you learn the Awful Truth of where sugar comes from in this world.)
The Deep Sleep Trilogy features a woman named Felicity at the very end of the second game who is described as this trope. She went insane because Her mind lost connection to her sleeping body and she can never again wake up, thus leaving her trapped for years.
Parodied in a Halloween Episode of The Simpsons, with Bart's Evil Twin, Hugo, locked up in the attic. The Twist Ending was that Bart was the Evil Twin, so Hugo was allowed to go free (even though he was clearly insane - then again, you'd be insane too, if in his shoes) and Bart is locked up in his place.
The Animaniacs are a parody example that got loose. The town tries to lock them in the old watertower repeatedly, but they just keep escaping using Cartoon Physics. And where would we be now without them, hmm? United States, Canada, Mexico, Panama....
Implied that the Morgendorffers in Daria had moved into a house that had one of these. Daria actually picked the room with the padded walls. Course, we don't get to see that.
The Oblongs do this to Granny. Sort of. Their son isn't even aware Granny is still alive.
In an episode of The Critic, a grizzled sailor tells Geraldo that the Shermans keep a hideous child locked in their basement (read: Jay) and points to a lumpy shadow to prove it. Geraldo, not buying it, immediately recognizes the shape as a sack of potatoes.
Allegedly actually happened (hopefully not anymore); A program on old houses featured a new homeowner doing research into a recently-purchased 19th century house, trying to determine the purpose of a second-story room with iron bars on the windows, a metal floor with welded metal loops for attaching chains, and a door that locks from the outside. While researching at the library, an old woman overheard him describing the room, tapped him on the shoulder, and gently explained to him, "You have a Disappointments Room," where children with developmental disorders were kept by families that didn't know what else to do, and didn't want their secret known. Further research turned up the former owner's family gravestone at the local cemetery; there was one name, a girl's, and a set of dates indicating death at a young age, that did not correspond to any of the family members listed in the town's archives.
A few supposed 'feral children' were locked up and isolated from human contact at a very young age, possibly because they were already a bit odd. The abuse doesn't exactly help.
Then there is the tale of "Genie" Genie spent her entire childhood locked-up and tied to a potty after her father (who wasn't the pillar of sanity himself) learned she was "mildly retarded" and blew it out of proportion. When she was rescued, it was discovered that she could not speak and she had a distinct "bunny" walk.
Feral child Dani Lierow, rescued at age seven after having been confined in her house and severely neglected, has been adopted and is growing up with her new family.
Kaspar Hauser, something of a Trope Codifier for the feral child version, claimed to have been locked up in this fashion for somewhat vague reasons possibly related to being the illegitimate son of someone famous. The general consensus nowadays is that he was making the whole thing up to scam people.
The legend of the Monster of Glamis, which seems to have at least some factual basis.
John Langdon Down (of Down Syndrome fame) advised against this in his writings, arguing that institutionalization was more humane, and that isolation and lack of education tended to make mental defects worse.
Supposedly the Lemp Family—founders of the now-defunct Lemp brewery—had a a son who was born deformed. He was known as the Monkey Boy, and kept locked in a cage suspended ten feet off the ground, deep in the caverns under the brewery. The cage is still there.
At points in the history of treating mental illnesses and syndromes, this has been the humane option—for reasons varying from the then-current State of the Art ideas of mental illness to modern, enlightened laws that make it impossible to permanently institutionalize many of those who are only functional in an institution. It mostly takes being disabled to the point of not being legally responsible for yourself, or having killed a few people the last time you stopped being functional.
Patrick Henry kept his wife in their Virginia basement for the last four years of her life, feeling it was more humane than the public hospital. Given that she would have had a windowless cell with chains and a chamber pot a the aforementioned hospital, he was probably correct.
King George V of England's youngest son Prince John (1905-1919) - who was epileptic and 'mentally feeble' (probably autistic) was rumoured to have had this done to him. The truth was that from about seven (when the expectation would have normally been for him to go to boarding school) he lived with his nanny 'Lala' Biggs (who, like many Edwardian nannies, seems to have been deeply bonded with her charge, more like a foster parent than a hired help) in a cottage in Sandringham Park, socialised with estate workers' children, and probably had a happier childhood than his healthy brothers. But because of the embarrassment of having a son with mental disabilities, his royal parents seem to have preferred to remain silent about his life rather than publicly address the rumours.
The infamous Elizabeth Báthory counts as one of these, as she was imprisoned within a bricked-up set of rooms, with only small slits left open for ventilation and the passage of food to the prisoner.