Newlyweds Bill Martin, Robin Thomas and Claire Martin, Starr Andreeff, move their new family into a house Bill built himself. Not long after settling in, Bill discovers a dollhouse in the shed that’s modeled after 112 Ocean Avenue in Amityville, New York. He brings the eerie keepsake into the home and parks it in the garage, a strange sense of unease settling over him. That night, the house’s fireplace seems to ignite on its own, heating every room, and Bill is troubled by a nightmare in which his daughter Jessica burns in the flames. The next morning, Claire finds the dollhouse again in the garage and suggests giving it to Jessica for her birthday, noting that their car had somehow rolled forward in the garage the night before, nearly striking the birthday present they had bought.
Jessica’s birthday gathering brings in Jessica’s Aunt Marla, Lenore Kasdorf, and Uncle Tobias, Franc Ross. Jessica is delighted by the dollhouse and discovers a chest full of miniature dolls inside it, but Aunt Marla and Uncle Tobias move with an unusual air of nerves around the toys, as if they know something that the others do not.
In the days that follow, a tide of strange occurrences washes over the family: Jimmy Martin, Jarrett Lennon, loses his pet mouse, which somehow finds its way into the dollhouse; at the same time, Jessica is menaced by an enormous white mouse that lurks under her bed. Claire begins to experience unsettling urges toward Todd Martin, Bill’s teenage son, during moments with Bill, casting a pall over their family life. Bill is haunted by nightmares of voodoo dolls, demons, and his family being murdered, a cycle that overlaps with childhood memories he suppresses. He confides in Marla that he had similar dreams as a child, including a premonition of his parents dying in a fire that later came true. Jimmy also begins to witness supernatural visits from his deceased father, who appears to him as a decaying zombie urging him to harm Bill.
One afternoon, Todd brings his girlfriend Dana, Lisa Robin Kelly, to the property. In an exterior shed, they uncover newspaper clippings about the foundation of the new home and realize the house was built around the fireplace from the original structure. The couple’s discovery leads them to a dangerous moment as they begin to have sex, but a large fly attacks Todd’s ear. The next evening, Bill and Claire go out for dinner, leaving Todd to babysit Jimmy and Jessica. Todd invites Dana over and sends the children to bed. While Todd mixes cocktails in the kitchen, Dana’s hair suddenly bursts into flames, leaving her in a coma with serious burns. Todd blames his father for the accident, suspecting a faulty coil in the fireplace’s gas line.
Meanwhile, Marla and Tobias, who practice occult arts, take one of Jessica’s dolls from the dollhouse and perform a ritual that animates the figure, giving it a demonic life identified as Gamigin. Objects begin to fly around their home, injuring Marla, and Tobias stabs the doll with a knife, pinning a large fly. Claire later finds a bruise on Jimmy’s face and suspects Bill; Jimmy tries to tell her that his father intends to kill Bill, but she refuses to believe him. The family is frightened when the zombie of Claire’s deceased husband appears, restrains them, and forces them to sit by the fireplace. Bill tries to enter the house through the garage but is knocked unconscious by carbon monoxide emanating from his car, which seems to start on its own.
Tobias arrives just in time to rescue Bill, and the two make their way back inside with the voodoo doll in hand. They confront the looming threat as they battle the zombie; Tobias urges Jimmy to fetch the doll, and Jimmy throws the voodoo doll into the fireplace, causing the zombie to vanish. Todd is visited by an illusion of Dana in the hospital, and she tries to kill him, but Claire intervenes. The family attempts to flee, but Jessica is nowhere to be found. A notebook filled with Jessica’s observations about the dollhouse reveals one startling line: “My hand disappears in the fireplace.” Bill realizes the fireplace is a portal to another place, and he and Tobias plunge into it to locate Jessica. They find her on the floor, surrounded by the bloodied remnants of the filled voodoo dolls. Tobias casts a protective spell, enabling Bill and Jessica to escape, but he is dragged away by the demons fleeing from the dolls, Gamigin among them.
Bill uses the dollhouse’s energy to destroy it by tossing it into the fireplace, and the family flees in their car as the house explodes behind them, the danger finally receding as they drive into an uncertain daylight.
