Sanity Slippage / Live-Action Films

aka: Film

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• Abandoned Mine: Round the middle part of the movie, Laurie starts making rather absured claims about the mine. She ultimately states that the mine is in fact a giant monster, and they're in its digestive system.
• Accident: Following Fatty's death (which he is convinced was aimed at him), the Brain begins a rapid descent into paranoia: seeing conspiracy at every turn.
• A.M.I.: Artificial Machine Intelligence: Cassie's sanity starts going downhill after A.M.I. starts hypnotizing her into killing people. By the end of the movie, she's surrounded herself with phones programmed to sound like her parents, her boyfriend, and a baby, and treats them all like they're real people. So, yeah, safe to say she's completely lost it at that point.
• In the documentary Hearts of Darkness: A Filmmaker's Apocalypse, which chronicles the Troubled Production of Apocalypse Now, director Francis Ford Coppola summarizes: "There were too many of us, we had access to too much money, too much equipment, and little by little we went insane."
• In The Assassination of Richard Nixon Samuel Byck (who was a real person) experiences this. Initially he just seems like a slightly delusional loser, but eventually he plans to hijack a plane and fly it into the white house. Not to mention his intentions of killing his boss before that.
• Assassin's Creed: Callum, due to having to be dragged into the Animus the first two times, starts hallucinating his ancestor severely enough to spar with him, as well as going Laughing Mad for a while. There's also the other Assassins who are left catatonic due to being forced into the Animus against their will.
• Backstage: Lucie wasn't all that rational about her passion for singer Lauren Waks and her songs to begin with, but her obsession morphing into Celeb Crush once she gets into Lauren's inner circle, to the point of interferring in her love life, only gets worse over time.
• This trope is the whole point of Black Narcissus. All of the nuns find their flaws and emotional weaknesses slowly becoming more and more exaggerated. Things are worst with Sister Ruth, none too well to begin with, who turns into a Stalker with a Crush, and winds up dying a Disney Villain Death when she attempts to murder her superior, Sister Clodagh.
• In Blood Harvest, Gary says that his brother Mervo was always odd, but he used to be fairly well-adjusted, even after the Career-Ending Injury that stopped him from working as a trapeze artist. But when the family lost the farm, all the animals were slaughtered, including Mervo's beloved pig Beulah. Mervo coped with the loneliness and grief by retreating further and further into his clown world until there was almost nothing left of his original personality.
• Francesco Dellamorte-Dellamore in Cemetery Man — this is, in fact, the whole plot of the film.
• In Cross of Iron Steiner goes through this as he's recovering in hospital. Even more so in the ending when he goes into a laughing fit in the middle of battle after Captain Stransky asks him how to reload his firearm.
• The Dark Knight: Harvey Dent screaming in silent agony in the hospital after realizing that Rachel died. From there his Sanity Slippage following The Joker's disturbing Breaking Speech.
• In The Dead Center, Dr. Forrester's sanity clearly took a hit when the demon briefly attacks him for the first time. He's left with flashing hallucinations of previous victims and is basically a nervous wreck. He's still well enough to function and beat Michael Clark to death, but how much sanity he has left by the end of the movie is debatable.
• Mike in Deep End suffers this, mostly courtesy of Susan. The entire plot of the movie is Mike becoming her Stalker with a Crush — except it's rather hard to understand why, considering her personality — and in the end his sanity finally snaps completely and he kills her. Given how she treated him throughout the entire movie, it's hard to sympathize with her.
• The Descent is a British horror film about a traumatised woman named Sarah who goes spelunking with some friends in the Appalachians, but then they get trapped in a cave-in. When things go From Bad to Worse and the party discovers that the cave is home to cannibalistic degenerates, the women descend into savagery to survive and Sarah completely loses it.
• In The Disappointments Room, Dana suffers this once the room is unlocked, thanks to the ghost of the judge.
• Gabriel from Drive, He Said subjects himself to Sleep Deprivation and drug abuse in an attempt at Obfuscating Insanity to avoid the draft. The stress takes such a toll on his mental health that he becomes a Conspiracy Theorist, moves to a campsite by a river, and eventually tries to rape Olive, then runs naked through the campus to free all the animals in the biology lab.
• General Jack D. Ripper goes through this as Dr. Strangelove unravels. He sends his base's squadron of B-52s to attack Russia, telling his attaché Group Capt. Lionel Mandrake that it's because Washington has been attacked. What Ripper eventually confesses is that he's impotent and that the Russians are responsible for it through fluoridation of the water. Everyone in the Pentagon war room (except, maybe, for General Turgidson) that Ripper went off his nut for pre-empting the failsafe mechanisms the attack plan called for.
• Elysium: Not that he was entirely sane to begin with, but Kruger becomes noticeably more unhinged following his facial reconstruction.
• Endless: Riley grows increasingly unhinged over her contact with and obsession over Chris. This convinces him that he has to let her go.
• Alex Forrest in Fatal Attraction grows increasingly unhinged the more Dan Gallagher tries to distance himself from her, until she reaches the point where she's willing to boil his daughter's bunny in the pressure cooker, kidnap her, and then try to knife his wife to death.
• Tim from Fragment of Fear is the target of a harassment campaign by a conspiracy that no one but him believes exists. He starts to lose his mind from stres and paranoia, until by the end he's hallucinating stalkers in empty seats.
• In Fury (1936), the hero undergoes a sanity slippage in the third act, caused by the guilt that is weighing heavily upon him. He starts hearing Katherine's voice when watching the shop window, he sees the number 22 on the calendar at the bar and can't help but think of the 22 accused. After he leaves the bar and walks along the street, he sees some of the faces of the mob in a store window. Frightened, he begins running down the empty road as if he's being chased, the camera follows him, only showing the audience what seems to be following Joe — nothing, only his conscience.
• In The Gamers: Hands of Fate, Gary continuously hallucinates horrible things about Chibichan, a Pokemon-esque creature, because its creation brought about the cancellation of one of Gary's favorite shows ever, Ninja-Dragon Riders.
• In The Hands of Orlac, Orlac's sanity starts to slip from the time he wakes up in the hospital with his new hands. He becomes possessed of the desire to kill and believes that along with the hands he has acquired the murderer's predisposition to violence. He decides he can no longer touch anyone with his hands lest he be overwhelmed by the compulsion to kill them. Things get worse as the movie goes on.
• In Werner Herzog's Heart of Glass, the death of a foreman glassmaker has deprived a 18th century glass factory of the secret recipe for red glass. The movie is driven by the factory owner, threatened by bankruptcy, progressively losing his already weak grasp of sanity.
• Hooded Angels: Ellie suffers a slow breakdown over the course of the move, becoming more and more bloodthirsty and unstable. It eventually reaches the point where Hannah realises that the only way to stop her will be to kill her.
• Horse Girl: Sarah starts off as a fairly normal if slightly eccentric woman, but over the course of the movie she becomes more and more out of touch with reality. Her missing memories and strange dreams intensify, she becomes more and more insistent on the reality of her theories about alien abduction and being a clone, and she becomes increasingly obsessed with bizarre, craft-supply based defenses against the aliens. She becomes more emotionally unstable as well, shedding her meek and understated demeanor from earlier on and becoming prone to anxiety and fits of hysterics.
• The main character in I Am Legend suffers the beginnings of sanity slippage, asking a mannequin to talk to him because he promised his dog he'd ask, then breaking down in tears because the mannequin does not answer. It's even worse in the deleted scenes/uncut version. When he drives past the mannequin trap the head of the mannequin actually moves, and when he wakes up after being saved from his suicidal assault, he first sees the people in his house as his own wife and daughter who had died years earlier.
• Joker (2019): The Joker undergoes considerable sanity slippage throughout the film, unsurprisingly. At the beginning of the movie, he is an already mentally unstable, struggling man who then deteriorates even more after experiencing multiple stressors around the same time as he loses access to both antipsychotic medication and therapy. By the end of the movie, his point of view becomes so skewed that it is unclear whether some events really happened or only happened in the Joker's mind. There are also whole scenes that definitely only happened in the Joker's mind, but some are left ambiguous.
• Jungle: Yossi's mental states is slowly degrading almost from the start of the trek into the jungle. However, once he is stranded by himself in the Hungry Jungle, he goes downhill rapidly. At his lowest point, he creates an Imaginary Friend to accompany him.
• In Killdozer!, Dutch starts losing it after Mac dies: first becoming paranoid and then telling long, pointless stories. By the end, he decides that he wants to go for a swim while the killer bulldozer is still on the loose.
• Eric in Killing Zoe wasn't exactly the sanest person to begin with, but doing copious amounts of heroin, murdering several people, and setting off some explosives cause him to become batshit insane. As further proof, one of his favorite threats towards the end are "I'll fuck your bitch up the ass and give her AIDS!"
• In Assamese anthology horror film Kothanodi (The River of Fables), the character Dhoneshwari descends rapidly into a delusional half-dream state where she imagines the python she married her daughter to is adorning her with jewellery on her wedding night, when it reality the python is eating her.
• Last Night in Soho: Eloise has visions of a girl called Sandie who lived through The '60s. At first, Eloise is fascinated, but her mental state begins to fracture as she discovers just how traumatic Sandie's life is. She completely loses it after witnessing Sandie's (apparent) murder, to the point of hallucinating in public and almost accidentally shanking Jocasta with a pair of scissors in a fit of insanity.
• In Let Us Prey Sgt. MacCready starts to lose it after Six reveals he knows that MacCready is a Serial Killer, becoming irritable and hostile. By the end of the film, he’s completely lost his mind, wrapping himself in barbed wire and going on a killing spree in the police station so he can “get back in touch with [his] Christian roots.”
• Although Trevor Reznik from The Machinist had been acting odd ever since he kills the boy, when he starts harassing and assaulting everyone around him in a paranoid conviction that they are all out to get him you can tell he has finally completely cracked.
• Mad Max: Fury Road:
  • Max certainly lives up to his name by this point. He's haunted by voices and hallucinations of the people he's watched die and failed to save over the years, most of all his wife and son, he twitches and mutters to himself often, and he shows signs that he's spent so long on his own that he's forgotten how to interact with people normally. These all point to signs of PTSD and schizophrenia.
  • On the villainous side, the Bullet Farmer starts out relatively understated and sedate, snarking about how they're committing dozens of cars to a "family squabble". After he's blinded, however, he begins ranting about he's the conductor of the Choir of Death, firing machine guns at nothing just because he enjoys shooting, and referring to his guns as "Brother Heckler" and "Brother Koch".
• The Man from Colorado: Four years of constant fighting and bloodshed have turned Owen into a Blood Knight. After the war ends, his sanity continues to erode and he becomes a Hanging Judge, finding an excuse to execute anyone brought before him, and he slides deeper and deeper into paranoia: eventually blockading the town to prevent anyone leaving and setting fire to part of it to flush out his imagined enemies.
• The Man Who Killed Don Quixote: Javier started losing his sanity when Toby was filming The Man who killed Don Quixote. And it progressively happens to Toby as well ten years later.
• Ms. 45: At first, Thana only kills men who attempt to take advantage of her. Later, as she loses more of her sanity, she kills any man unlucky enough to be near her.
• In Mulholland Dr. all it took to send the mentally unstable protagonist over the edge was some knocking on the door.
• My Life as a Dog: No, this movie is not about literal transformation into a dog. It is about a boy, Ingemar, and his ways of coping with life’s difficulties. After he suffers significant loss, he pretends he’s a dog to deal with his grief. He repeatedly brings up the story of Laika, the first dog sent into space and left to die, because he identifies with Laika’s journey—just as the dog was starved of food, so is Ingemar starved of affection.
• Next of Kin (1982): All the horrific events endured by Linda eventually take their toll on her mental well-being. The entire third act has her pretty much teetering on the edge of completely losing it as she is forced to defend herself from Kelvin and Rita.
• Mac in Predator, after Blaine's death.
• Zac Hobson in The Quiet Earth begins suffering this when he realises that he may very well be the last human being alive. After the Good-Times Montage, he begins dressing in women's clothes; he fills his garden with cardboard cutouts of celebrities; he fires his shotgun wildly at televisions; he declares himself President of the World and gives his inaugural address to the cutouts. And then the power goes out, leaving Zac standing on his balcony, in total darkness and utterly insane. He gets better.
• Reality (2012) is the story of the protagonist's descent into insanity, although it is hinted that he wasn't particularly stable to begin with.
• Repulsion is about a troubled young woman stumbling deeper and deeper into madness.
• Rituals:
  • Martin loses it after his leg is broken by a bear trap and loudly rants about how they're all being hunted as part of a demonic ritual. This is mainly due to a combination of being in massive amounts of pain and getting drunk to cope.
  • Harry does a valiant job of keeping it together, but he starts to crack after Martin dies and he's forced to Mercy Kill DJ. He snaps completely after Mitzi is killed and begins wildly firing a shotgun while demanding Matthew come out and face him man-to-man.
• Dr. Scott feels that's what is happening to him in "Don't Dream It, Be It" from The Rocky Horror Picture Show:
  Ach!^note CHOO! We've got to get out of this trap
  Before this decadence saps our wills.
  I've got to be strong, and try to hang on
  Or else my mind may well snap^note CRACKLE POP!
  And my life will be lived^note IN A BOWL OF RICE KRISPIES for the thrills.
• Stéphane in The Science of Sleep always had rather odd and confusing dreams and Imagine Spots to help his cope with reality... by the end of the film he's unable to tell the difference between the two. While it doesn't go all the way to the end he holds shades of this.
• In Séance on a Wet Afternoon, Phony Psychic Myra Savage has been gradually losing her grip on reality since the Tragic Stillbirth of her son Arthur, whom she never even got to see or hold as she was still coming round from the drugs. She initially seems to Cope by Pretending that he is alive, but it emerges that she thinks she is communicating with his spirit, who wants her and her husband Billy to kill the girl they have kidnapped so she can "be with him". In the film's final scene, she breaks down during a séance with two detectives, rolls up a cloth, and cradles it in her arms in a way she never had a chance to do with Arthur.
• Gordon in Session 9, although whether it's insanity or some sort of supernatural possession is left deliberately ambiguous.
• In Shine, David starts off reasonably normal but as time goes on becomes increasingly manic and starts being less intelligible, peaking when he plays Rachmaninoff's Third Piano Concerto and in the aftermath.
• Stonehearst Asylum: Lamb. While his methods towards mental health are humane in and of themselves, he keeps the real staff locked up, puts a homicidal killer like Finn in charge of security and shows no remorse when Finn kills two escaped staff members and later one of the patients, electroshocks Salt into amnesia, and tortures Newgate.
• Adele Hugo in The Story of Adèle H. Adele suffers from schizophrenia, which manifests in the form of erotomania towards the object of her affection, Pinson. As he continually rejects and avoids her, her mental condition worsens, leading her to grow increasingly desperate and deluded as she starts calling herself his wife ("married in spirit") and sabotages his relationships. Her obsession makes her ill and eventually she begins wandering the streets while talking to herself. After following him to Barbados, her mental condition is so deteriorated that she eventually ceases to recognize him and she wanders the streets in torn, ragged clothing.
• In Thor, Loki's sanity starts to slip after he discovers his true Frost Giant heritage. By the time he is fighting Thor at the end of the film, he is on the verge of Laughing Mad and has clearly taken a dive off of the slippery slope. The slippage continues into The Avengers, where it's clear that his fall through the Bifrost has left him Ax-Crazy and more than a little unhinged.
• The documentary Touching The Void is about the two climbers Joe Simpson and Simon Yates in their attempt to climb the Siula Grande mountain. After Joe Simpson has had his rope cut, and has been days without food or water, he eventually becomes delirious; as he presumes himself to be close to death, the song 'Brown Girl in the Ring' by Boney M gets stuck in his head, which is a song that he hates.
• In Tower of London (1962), Richard III's sanity begins to crack from the time he commits his first murder until, by the end of the movie, he is completely paranoid and haunted by visions of everyone he has killed.
• It is a thing to behold when this happens to Alonzo Harris towards the end of Training Day, when he finally realizes that his corrupt methods held no power over anyone any longer, and he was truly going to die.
• In the classic The Treasure of the Sierra Madre, Dobbs becomes increasingly unhinged as greed and paranoia brought on by Gold Fever sets in, eventually leading him to try to murder everyone in his group.
• Vampire's Kiss is the story of Nicolas Cage's character, the businessman Peter Loew, slowly becoming crazy, firmly convinced he's turning into a vampire.
• A View to a Kill: While he was already mentally unstable, Max Zorin loses whatever sanity he had as the film progresses. After Bond foils his scheme to trigger an earthquake in the San Francisco Bay Area to corner the microchip market, Zorin goes nuts to the point of gunning down his minions out of pure sadism and wildly swinging a literal axe against 007 during their showdown. A justified trope, as Zorin is the end result of a Super Breeding Program to create the ideal Super-Soldier for the Nazis Gone Horribly Right — while most of the pregnancies failed, the few babies that survived became gifted later in life — but also totally psychopathic.
• Happens to Komodo in Warriors of Virtue after he kills Master Chun. Although he was pretty zany from the start, he seemed to drop a few notches after the event.
• Weekend at Bernie's: Paulie the hitman gets progressively more unhinged as he futilely chases the oblivious protagonists, and is finally dragged away in a straitjacket, yelling that his victim Bernie is still alive.
• The central plot of A Woman Under the Influence. Mabel, a psychologically fragile housewife, has a full-on breakdown brought on by the pressures of motherhood and the stress of being married to a mean, aggressive husband. Early in the film she is doing odd things like addressing people who aren't there or calling people by the wrong name. Eventually she's committed to an asylum.
• In X-Men: The Last Stand, this is why Xavier had neutered Jean Grey's mental powers to keep the Phoenix hidden. And once she's unleashed...

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