The Man in the Planet is moving levers in his home in space, while the head of Henry Spencer floats in the sky. A spermatozoon-like creature emerges from Spencer's mouth, floating into the void.
In an industrial cityscape, Spencer walks home with his groceries. He is stopped outside his apartment by the Beautiful Girl Across the Hall, who informs him that his girlfriend, Mary X, has invited him to dinner with her family. Spencer leaves his groceries in his apartment, which is filled with piles of dirt and dead vegetation. That night, Spencer visits X's home, conversing awkwardly with her mother. At the dinner table, he is asked to carve a chicken that X's father has "made"; the bird moves and writhes on the plate and gushes blood when cut. After dinner, Spencer is cornered by X's mother, who tries to kiss him. She tells him that X has had his child and that the two must marry. X, however, is not sure if what she bore is a child.
The couple move into Spencer's one-room apartment and begin caring for the child—a swaddled bundle with an inhuman, snakelike face, resembling the spermatozoon creature seen earlier. The infant refuses all food, crying incessantly and intolerably. The sound drives X hysterical, and she leaves Spencer and the child. Spencer attempts to care for the child, and he learns that it struggles to breathe and has developed painful sores.
Spencer begins experiencing visions, again seeing the Man in the Planet, as well as the Lady in the Radiator, who sings to him as she stomps upon miniature replicas of Spencer's child. After a sexual encounter with the Beautiful Girl Across the Hall, Spencer has another vision, seeing his own head fall off, revealing a stump underneath that resembles the child's face. Spencer's head falls from the sky, landing on a street and breaking open. A boy finds it, bringing it to a pencil factory to be turned into erasers.
Awakened, Spencer seeks out the Beautiful Girl Across the Hall, but finds her with another man. Crushed, Spencer returns to his room, where the child is crying. He takes a pair of scissors and for the first time removes the child's swaddling. It is revealed that the child has no skin; the bandages held its internal organs together, and they spill apart after the rags are cut. The child gasps in pain, and Spencer stabs its organs with the scissors. The wounds gush a thick liquid, covering the child. The power in the room overloads, causing the lights to flicker; as they flick on and off the child grows to huge proportions. As the lights burn out completely, the child's head is replaced by the planet seen at the beginning. Spencer appears amidst a billowing cloud of eraser shavings. The side of the planet bursts apart, and inside, the Man in the Planet struggles with his levers, which are now emitting sparks. Spencer is embraced warmly by the Lady in the Radiator, as both white light and white noise build to a crescendo before the screen turns black and silent.
