Donny Kohler Dan Grimaldi is a withdrawn man in his thirties who is obsessed with fire—a fixation rooted in a cruel childhood, when his sadistic mother, Mrs. Kohler Ruth Dardick, would burn him on the gas stove to “burn the evil out of him.” After returning from his factory job to the dilapidated Victorian home he shares with his now-elderly mother, Donny discovers she has died in her upstairs bedroom, a moment that floods him with relief and fear as he begins to hear a disembodied voice that seems to be hers.
The next day, he calls in sick and spends the afternoon lining an upstairs room with aluminum, turning it into a fireproof chamber. That night, he visits a flower shop just before closing and is helped by Kathy Jordan Johanna Brushay, who sells him flowers for his mother. Outside, Kathy misses her bus and is harassed by a group of men. Donny offers her a ride; she accepts, and he talks her into meeting his mother, though she grows nervous once inside and tries to call a taxi before he incapacitates her.
Kathy regains consciousness to find herself naked and chained to the ceiling of the metal-walled room. Donny, donned in a fire suit, douses Kathy with gasoline and burns her alive with a flamethrower. The following day, Donny calls in sick again and abducts a stranded female motorist, killing her by immolation. He then eerily dresses his mother’s corpse in her clothing and proceeds to mimic his earlier ritual, repeating the pattern with Linda, a woman he assaults at a grocery store, and arranging her beside the other three victims and his mother.
Donny’s friend Bobby [Robert Carnegie] phones to warn him that their boss will fire him if he misses work again. Meanwhile, Donny is haunted by apparitions of his burnt mother, who seems to stalk him inside the house. He spends hours regaling the four corpses, whom he has posed in chairs in a bedroom, with stories from his life. Overwhelmed by guilt, Donny seeks counsel from Father Gerritty [Ralph D. Bowman], the local priest, confessing that his mother repeatedly burned him to purge the supposed “evil” within him.
Later, Donny accepts Bobby’s invitation to go on a double date at a disco. When his date tries to pull him onto the dance floor, she brushes his arm against a lit candle, triggering memories of his abuse. Enraged, Donny hammers the candleholder onto her head, setting her hair on fire. He flees the disco and lures two drunk women back to his home. Bobby and Father Gerritty hurry to Donny’s house, break down the door, and rescue the two women. Donny locks himself in his mother’s bedroom as the voices express their disappointment; the burned corpses come to life and attack him, and he dies as the house burns around him, dragged to the floor by his macabre audience.
Sometime later, a young boy named Michael watches a news report about Donny’s death. His mother chastises him for not turning off the television and sends him upstairs to clean his room. When she leaves, Michael hears the same voices that haunted Donny, and they tell him they have come to help him.
