Henry Spencer lays on his side with a planet in outer space floating behind his head. The interior of the planet houses a deformed man looking out a window. A ghostly worm-like creature emerges from Henry’s mouth. When the disfigured man pulls a lever, the creature skitters away and falls into a hole of water. Henry appears at the other end of the hole. He walks through a deserted industrial landscape until he arrives at his apartment building. As Henry enters his apartment, the beautiful girl across the hall gives him a message from a woman named Mary: Mary and her parents invite Henry to dinner. That night, Henry walks to Mary’s home. When Mary greets him at the door, Henry asks her why she doesn’t come around anymore. Inside the house, Henry meets Mary’s mother, Mrs. X, who asks him what he does for a living. While Henry explains that he’s on vacation but works as a printer by trade, Mary has a fit. Mrs. X calms her daughter by combing Mary’s hair. Mary’s father, Bill, announces they’re having tiny man-made chickens for dinner. As they sit down to eat, Bill mentions that he got an operation that left him with the ability to move his arm, but he has no sensation in the limb. Bill asks Henry to carve the tiny chickens. Henry starts to carve but the roasted chicken moves its legs on its own as blood pours out of the cavity. Mrs. X has a fit, then runs into the kitchen. Mary runs after her. When Mrs. X returns to the dining room, she takes Henry aside and asks him if he and Mary had sexual intercourse. She explains that Mary gave birth to a premature baby and Henry is the father. While Mary protests that the doctors aren’t sure whether it really is a baby, Mrs. X insists that Henry and Mary get married and then pick the baby up from the hospital. Henry gets a nosebleed and agrees to wed Mary. Later, while Mary is alone in Henry’s apartment, she tries to feed their baby -- a small, swaddled, nonhuman creature -- but it keeps spitting at her. Meanwhile, in the lobby, Henry goes to his mail slot and takes out a small box containing a tiny live worm. Henry enters the apartment and expresses happiness when he sees Mary feeding the baby. Henry watches the radiator as it is suddenly illuminated from within, revealing a tiny stage inside. That night, while Mary sleeps, Henry gets out of bed, takes the worm out of the box, places the worm in a cabinet and returns to bed. As the baby continues crying, Mary yells at it to be quiet. She gets dressed and announces to Henry that she’s going home to get a decent night’s sleep. Mary tells Henry that he can watch the baby for a night since he’s on vacation. As she leaves, Mary warns Henry that he had better take really good care of the baby until she gets back. In the middle of the night, Henry gets up to take the creature’s temperature. The thermometer reading looks normal, but when Henry looks back at the baby, it is covered in strange growths. He realizes the baby is sick and turns on the vaporizer. The baby sleeps fitfully while Henry returns to bed and watches the radiator. A woman with large, deformed cheeks dances on the stage inside the radiator. She shares the stage with several of the slimy worm-like creatures that she crushes under her feet as she dances. Sometime later, Henry is lying in bed with a feverish, sweaty Mary and finds several worm creatures in the bed. He throws them against the wall. Meanwhile, the cabinet doors open and the worm Henry that placed in there earlier crawls out. One end of the creature opens into a mouth. Inside the mouth, Henry appears alone, sitting on his bed when he answers a knock at the door. He lets in the pretty girl from across the hall who has locked herself out of her apartment. As the baby whimpers, Henry covers its mouth with his hand. When the young woman asks where Henry’s wife is, Henry realizes Mary must have gone back to her parents; but he’s not sure where she is. The girl asks if she can spend the night. Later, as Henry and the girl have sex on his bed, they slowly descend through a cauldron of water. She seems frightened when she looks around and sees the planet. Inside the radiator, the deformed woman on the stage sings about how everything is fine in heaven. Henry approaches her on the stage. As he touches her hand, he hears music and sees a white light. When the light fades, however, Henry is invisible to the woman and she is invisible to him. Suddenly, the woman is replaced by the deformed man. On the stage floor, the worm creatures are blown away by a strong wind. Then a large rock with a tree in it rolls onto the stage. Suddenly, Henry’s head pops off his body and rolls on the floor. Blood pours out of the rock and pools around Henry’s head. A creature similar to the baby emerges from Henry’s neck and starts wailing. Henry’s head falls through the stage, drops into an outdoor location and hits the pavement. A boy picks up the head and runs to a factory where a workman drills a pencil into the skull. The man removes the pencil and places it on a conveyor belt with other pencils. When it comes out the other end of the conveyor belt, the workman announces that the pencil is acceptable and he pays the boy for the head. Henry wakes up in his bed. Later, he knocks on his neighbor’s door, but she doesn’t answer. The baby laughs at him. Henry lies down on his bed, then goes to his door again and sees the young woman who lives across the hall taking a man into her apartment. She has a vision of the headless Henry with the worm coming out of his neck. Henry shuts his apartment door, gets a pair of scissors and cuts the swaddling off of the baby. As it shivers, agitated, the covering falls away, exposing the creature’s internal organs. Henry stabs the organs with the scissors. Blood and other fluids spurt from the organs and from the creature’s mouth. Then a chunky foam oozes out and envelops the creature. The lights in the apartment flicker and Henry suddenly sees that the head of the worm creature has become enormous. The head lunges for him as the lights go out. A hole cracks open in the planet. At the other end of the hole, the deformed man sits near the window, pulling and pushing levers. The deformed singer from the radiator approaches Henry and, as he sees a blinding white light and hears a cacophony, he and the woman embrace.