The story is about a scientist named Crawford Tillinghast who has invented a machine that — partly by stimulating the pineal gland — allows its users to see the vast and terrible layers of reality that coexist with the world perceived by the five senses.
As the film opens, Tillinghast (Jeffrey Combs) activates the "resonator" (basically four large tuning forks connected to a giant computer), which glows hot pink and allows him to see eel-like creatures floating in the air. One of the creatures attacks him; he shuts the resonator off and runs to tell his mentor/collaborator, the kinky Dr. Pretorius (Ted Sorel).
Pretorius cranks the machine up to 11 and revels briefly in all the new sensations it gives him. Then something eats his head.
Tillinghast is charged with Pretorius' murder and confined to a mental institution. But "girl wonder" psychiatrist Dr. McMichaels (Barbara Crampton) sees a pattern in Tillinghast's ravings and suspects he may be telling the truth. She has him released into her custody and the two of them, accompanied by a policeman (Ken Foree), return to the house where the whole mess went down.
Repeated experiments with the resonator bring Pretorius Back from the Dead with a fresh new attitude and a few extra appendages, make McMichaels the recipient of the most revolting screen "kiss" ever (and later induce her to don some fetishwear that happens to be lying around), and leave Tillinghast bald, traumatized, and covered in goo.
When the resonator is switched on (extradimensionally, by Pretorius) for the last time, Tillinghast's pineal gland pushes through his skull and pops out of his forehead on a stalk. Transported to a hospital, he goes on a brain-eating rampage which eventually takes him back to the house, where he tries to de-brain McMichaels as she attempts to blow up the machine. She counters by biting off his gland in a scene nearly as gross and fully as symbolic as her kiss from Pretorius.
Finally, Pretorius and Tillinghast battle one another to the gooey, gory death. McMichaels succeeds in destroying the laboratory, but when she tries to tell her story she is confined in the very institution at which she used to work. So it goes.
The film provides examples of:
- Adaptational Heroism: Crawford Tillinghast in the short story was driven mad by obsession, and fed his own servants to the creatures from "beyond". In the movie, he's the hero, and is repulsed by Pretorius and his experiments.
- Adaptation Expansion: The short story is about seven pages long, and describes a single operating run with the machine. It has only two onscreen characters, Tillinghast and the unnamed narrator. The movie's Tillinghast is a Composite Character of those two; every other character in the film, and most of the plot, is new.
- Another Dimension: There's another dimension that's a scary place.
- Beast with a Human Face: Pretorius after he comes back wrong.
- Big Electric Switch: The Resonator is activated by throwing one of these switches.
- Bittersweet Ending:
- Pretorius has been destroyed, but Tillinghast is also dead and Dr McMichaels is committed against her will and prepped for electric shock therapy.
- And that's the upbeat interpretation. Alternately, if one assumes the explosion knocked out the device before it reached what was left of Pretorius/Tillinghast, it's a full-blown And I Must Scream Ending for the latter...
- Black Dude Dies First: With a nickname like "Bubba", this was inevitable.
- Blob Monster: Pretorius after he comes back wrong.
- Body Horror:
- Pretorius gets his head bitten off by fourth-dimensional eels and later shows up as a mass of pink goo with a face and tentacles.
- Crawford has his pineal gland extend through his forehead (the pineal gland is located near the back of the brain) and later bitten off.
- The two merge during the final battle.
- Bondage Is Bad: The deviant Dr. Pretorius is revealed to have been way into BDSM when the main characters discover his secret dungeon after his disappearance. It's a sign that Katherine is starting to lose her mind when she suddenly gains an interest and tries out one of the costumes.
- Came Back Wrong: Pretorius, oh so much. He's become a barely human mutant... "thing" on the other side.
- Chalk Outline: Pretorius's is marked on the lab's floor when Crawford returns there, complete with a tapered neck-stub in place of a head.
- Cosmic Horror Story: When an overambitious scientist builds a machine that connects our world with the Outer Darkness - and tests it on himself - you know nothing good is going to happen.
- Dr. Jerk: Dr. Bloch.
- Eaten Alive: Bubba is devoured living by the creatures from the other side. Not Swallowed Whole either, more like all the meat being stripped from his bones.
- Eldritch Abomination: The leechlike things that appear when the resonator is turned on.
- Eye Scream: At one point, an eyeball is sucked out of a woman's head and her frontal lobe is consumed through her eye socket. There's also several instances of people's third eyes bursting out of their foreheads on stalks, and these eyes are occasionally subject to injury themselves. Even in the opening scene, the extradimensional eel-thing that attacks Crawford dives straight at his left eye.
- Fan Disservice: Barbara Crampton in a strategically torn nightgown, getting her head sucked by an extradimensional pervert.
- Fanservice: Barbara Crampton in a leather corset.
- Groin Attack: Crawford knees a female nurse in the crotch, while trying to suck her eyeball out to get to her brains. Ew.
- Heroic Sacrifice: Crawford fights Pretorious, resulting in his being eaten by the once-human monstrosity and tearing his way through, in order to buy Katherine time to plant the bomb on the Resonator and escape.
- Humanoid Abomination: It's pretty clear when we see him after his first "death" that the only things still remotely human about Pretorius are his sexual deviancy and his face.
- Idiot Ball: After the trio survive the first encounter with Pretorius and shut off the resonator, Katherine proclaims that they must try the experiment again. Naturally Crawford and Bubba are horrified by the idea.
- Jerkass Has a Point: The doctor in charge of the mental facility, Dr. Bloch, may treat Dr McMichaels harshly in her interactions with her but most of her criticisms are completely valid.
- Lamprey Mouth: The giant worm-thing in the cellar.
- Laughing Mad: Katherine, at the very end.
- Living Motion Detector: The "things." At one point Katherine uses this to her advantage, thrashing wildly in order to induce them to bite off her restraints.
- Lovecraftian Superpower: Dr Pretorius, after getting his head torn off, comes back as a Humanoid Abomination. He takes entirely too much pleasure in abusing his newfound powers, manifesting forms that would give The Thing a real run for its money in the Body Horror department.
- Mad Scientist: Dr Pretorius.
- Man Bites Man: The heroine chews off one of her monster boyfriend's tentacles.
- Nightmare Fuel Station Attendant - Initially at least, Katherine is intrigued by the resonator's effects and wants to continue experimenting with it, despite witnessing Pretorious make his own face explode on purpose.
- Off with His Head!: Dr Pretorius gets his head torn off by fishlike ... things from Another Dimension.
- Only Sane Man
- Naturally, nobody believes Crawford Tillinghast's story of strange creatures existing out of phase with us that can be seen when our pineal glands are stimulated. He is taken for a schizophrenic and rightly so. Inverted later when Dr. Katherine McMichaels who believes Crawfords story and wants to continue his experiments against his and the accompanying police officer's protests.
- Later, Bubba becomes the voice of reason in response to the traumatized Tillinghast and the junkie-like Katherine
- Orderlies Are Creeps: A Sadist orderly who preps Katherine for shock treatment.
- Orgasmatron: While the resonator's intended purpose is to stimulate the pineal gland, it also comes with a side effect which stimulates something else. Bubba comments on having gotten a hard-on when the machine was turned on, and upon activating it herself, Dr. McMichaels very forcefully kisses Crawford and later dons a leather corset to mount him while he's sleeping.
- Phlegmings: Every monster, but particularly the bat creature at the end.
- Pineal Weirdness: The mad scientist stimulates his pineal gland, allowing him to see into other dimensions. Freshly put to use, it grows to the extent that it pops out of his head on a stalk. To the further amusement of anyone familiar with brain anatomy, as the stalk extends in front, yet the pineal gland is near the back of the human brain.
- Shout-Out: Dr. Bloch is an obvious reference to Robert Bloch, who Lovecraft corresponded with over the years.
- Spiritual Successor: To Re-Animator. It has the same director, two of the lead actors, and many of the same crew, adapting another story by Lovecraft.
- Swallowed Whole: Tillinghast is in the process of being swallowed from the neck up by a giant worm-creature when Bubba turns off the Resonator to banish it back to its home dimension. Tillinghast comes away from it with his life, but he loses his hair in the process.
- Title Drop: "He's trying to start the resonator... from beyond!"
- Vein-o-Vision: Tillinghast's Horror Hunger and altered perceptions lead to him getting Brain-O-Vision, and "seeing" the tasty brains inside peoples' skulls.
- Vomiting Cop: Bubba turns away and vomits after Pretorius appears to the trio for the first time.
- Was Once a Man: Dr Pretorius after he comes back wrong.
- Weirdness Censor: We're surrounded, every second of every day, by bizarre entities doing bizarre things. Our senses are simply not made to perceive them. Normally, theirs aren't either. It's better that way.
- What Happened to the Mouse?: Bubba is shown carrying a weightlifting bar with his belongings when they arrive at the house but it's never seen being used or handled after that.