In 1892 New England, Rufus Sinclair suffers from catalepsy and lives in fear of being pronounced dead and buried alive. To prevent this, he leaves detailed instructions to the family and his staff, but when he is found, his greedy family—eager to claim their inheritance—have him quickly interred. Rufus leaves specific instructions on how to be buried, which are violated and the family lawyer, while reading the will, lets them know they will die from what they fear most:
Bruce will have his face disfigured; the widow Abigail will die by fire; asthmatic and alcoholic son Philip will suffocate; Philip's frustrated wife Vivian will drown; faithful manservant Seth will "join me in my tomb"; and all-around-nice-guy nephew James will lose that which is most dear to him, his pretty wife Deborah.
Abigail reveals she left a diamond brooch on Rufus's coffin, Bruce, needing the money, and family maid and lover Lettie recover it, though Bruce is perturbed to find it on the floor. He leaves Lettie at the crypt against her wishes, saying they need to return separately—and she is beheaded by a masked killer—seemingly Rufus returned from the grave. He leaves the head to be discovered by Bruce and others on a dinner tray. Bruce vows to stop Rufus while forcing Vivian to help him.
Bruce is maimed in the face by the masked killer—who then drags him to his death behind a horse. Vivian reveals that Lettie was murdered; Seth tells the remaining family members that Bruce's corpse is at the stable. Phillip finds Abigail's diamond pin on Bruce's body, and Abigail runs away in tears. The family lawyer sends Robert into town for the police. Phillip is named the new family patriarch and vows to do his best. Abigail says she's glad Rufus is alive so he can pay for the two murders. Seth feels he's in the clear, until Phillip reminds Seth that he violated the terms of the will and is "one of them now."
The police arrive, and Phillip informs him that the family believes Rufus was buried alive. The lawyer agrees and says that Rufus will now be totally insane. Phillip and the rest of the family give the police Rufus's description, and the police vow to find him. After Abigail has a panic attack, Phillip stays with her on her request, but then ducks out to get a drink, which he shares with one of the policemen. They get drunk, and Phillip tells him that Abigail has a morbid fear of fire. The masked figure later enters Abigail's room, chloroforms her, binds her to the bed—and sets her aflame. The family is unable to save her. The men then search with dogs, leaving Vivian and Deborah at the house.
Seth enters the crypt, apologizing for failing in his task of lighting the torches. He attempts to do so, and is murdered when the figure pulls a sword from the cane, fulfilling the will's threat he would die in the crypt. Deborah convinces Vivian that they should dress up for Phillip and Robert. Phillip and Robert wander from the search party and Robert finds Seth's corpse.
The masked killer knocks out the policeman on guard and then strangles Vivian while she's bathing. Deborah walks in, and the masked killer drags her away to the bog. Robert chases after them. The killer is revealed to be Phillip, upset with his treatment by his father and the rest of the family, the forgotten child. Phillip says he did not wish to kill her, but must now. Robert arrives and the two fight. Robert gains the upper hand, and Phillip sinks into the bog—dying as the will foretold.
Robert and Deborah leave happily. The two policemen decide to share Phillip's remaining booze, while lamenting over his ability to commit all the murders. They discover that the alcohol was merely tea, and that Phillip was not an alcoholic at all, just playing one so he could get away with the crimes.Helen Warren as Abigail Sinclair
Roy R. Scheider as Philip Sinclair
Margot Hartman as Vivian Sinclair
Robert Milli as Bruce Sinclair
Hugh Franklin as James Benson
Jane Bruce as cook
Candace Hilligoss as Deborah Benson
Dino Narizzano as Robert Harrington
Linda Donovan as Letty Crews
J. Frank Lucas as Seth Lucas
Paul Haney as Constable Barnes
George Cotton as Constable Winters
William Blood as minister
The film was shot in Stamford, Connecticut. Robert Verberkmoss served as art director.