Two adults and a juvenile burglar break into a house occupied by a brother and sister and their stolen children and can't escape.
Poindexter Williams, known as "Fool", is a resident of a Los Angeles ghetto. He and his family are being evicted from their apartment by their landlords, the Robesons. Leroy offers to plan a robbery of the Robeson's residence in order to get medical care for Fool's mother, who has cancer, and to get even with them. The Robesons, who refer to themselves as "Mommy" and "Daddy", live in a large home with their daughter, Alice, and their large dog, Prince.
Leroy and his associate Spenser take Fool to the house for reconnaissance, posing as a Bear Scout, but Mommy will not let him in. Spenser, posing as a municipal worker, gains entry, but arouses suspicion with Mommy. When the Robesons leave the home, Fool and Leroy became suspicious when Spenser doesn't return and decide to break in. Fool ventures into the dungeon-like basement and finds Spenser dead on the floor and a large group of strange pale children in a locked pen.
Terrified, Fool flees and reunites with Leroy as the Robesons return; Leroy is discovered and shot to death by Daddy, while Fool is drawn into another section of the house, where he meets Alice. She tells him that the people in the cellar are the former children of her parents who have disobeyed one of the three "see/speak/hear no evil" rules of the household. The children have degenerated into cannibalism to survive. Alice has avoided this fate by obeying the rules without question. She also tells him that one of the children, a boy named Roach whose tongue was removed for speaking evil, has escaped from the cellar and into the walls, evading Daddy.
Fool narrowly manages to evade detection with the aid of Roach, but is captured when he reunites with Alice; Roach escapes, but is shot in the process. He rescues Fool from the cellar after Daddy leaves him for the cannibals, giving him a small bag of gold coins and a written plea to save Alice before succumbing to his wound. Fool ascends the furnace chute to save Alice. Fool punches Daddy as he and Alice escape into the passageways between walls. Meanwhile, Daddy finds Roach's body in the furnace and cremates him. Daddy then releases Prince into the walls to kill Fool, which fails when Fool slams Prince against the wall and Daddy stabs through it, thinking it is Fool, but killing Prince instead. Fool and Alice reach the attic and find an open window above the garden pond, but Alice is too afraid to jump and Fool is forced to do so without her after Daddy discovers them. Fool climbs over the fence to freedom, but yells to Alice that he will return for her.
Once home, his grandfather Booker plans to sell the coins to pay for the family's rent and a life-saving operation for Fool's mother. He also tells them that the Robesons are not husband and wife but brother and sister, the last of a mortician family that built a fortune based on outrageous pricing and unscrupulous real estate deals. Greed and paranoia eventually drove them into inbreeding, and each generation has become increasingly unstable and psychotic. Fool alerts the police, and sneaks back into the house as the Robesons successfully hide their actions with a clever charade. After the police leave, they ambush him, but he manages to fight them off and climbs towards the attic, where he finds Alice bound to the chimney. Once informed that she and all of the other children now in the basement were kidnapped by the Robesons, she commits to helping stop them. Fool wants to escape the same way he did the first time, but Alice warns him that the minute Fool escaped, Daddy drained the pond and filled it with broken glass and rocks, sealed off many of the passageways, and wired the entire house with explosives. Fool is cornered by Daddy during a failed surprise attack, but is saved when Ruby, Booker, and other friends from their neighborhood converge on the house, distracting them enough for him to escape into the basement. The children held captive there, eager to assist an ally of Roach, take Fool to the vault, where the Robesons have stashed their enormous stores of cash and gold, as well as a stockpile of explosives.
Alice is cornered by Mommy, but the imprisoned children break out of the basement and chase her to the kitchen, where Alice is holding a butcher knife which Mommy runs into and impales herself on. Alice denounces her as her mother, and Mommy pulls the knife from her wound and attempts to attack Alice with it, but the escaped children converge on her and kill her, tossing her down the basement steps to land at the feet of Daddy. Distraught, Daddy tracks Fool to the vault, only to find that he has commandeered the detonating wires and threatens to blow up the vault; Daddy attempts a feint, and Fool sets off the explosives. The resulting detonation demolishes most of the house and blows the money up through the crematorium chimney and into the crowd of people outside; Daddy is thrown through the wall and into the waste pit, where he dies. Alice and Fool reunite in the basement, the people outside claim the money distributed by the blast, and the freed children venture into the night.Source: Wikipedia