PARANOIAC

After the wealthy Mr. and Mrs. Ashby die in a plane crash, their three children were left in the care of their Aunt Harriet. Three years later, the elder son, Tony, jumped into the sea when he was 15 after he had left a suicide note, but his body was never recovered. Eight years later, the younger son, Simon, is a cruel spendthrift alcoholic, who tries to have his sister, Eleanor, committed for insanity so that he can be the sole heir.

Only three weeks before he inherits, a man resembling an adult Tony appears. Initially, he is seen only by Eleanor, who believes that her dead brother is calling her from beyond the grave. She is rescued by him during a suicide attempt.

The man claims to be Tony and that he simply ran away. Eleanor believes him, but Harriet calls him an impostor. In fact, he is a conman, who was hired by Keith Kossett (Bonney), the son of the family attorney, to allow Kossett to keep embezzling from the estate.

"Tony" hears music from the family chapel at night. When he investigates, he is attacked by a masked figure with a hook. Eleanor heard the music before but was too afraid to leave her room. Simon appears to be open-minded about him but does not really believe him. Fearing that he will lose the inheritance, Simon sabotages the car when "Tony" and Eleanor go for a drive, and Eleanor is nearly killed.

That night, the music starts again. Eleanor and "Tony" investigate and see Simon playing the organ with a masked singer, but the singing emerges to be a recording. Eleanor is spotted by the masked person, who emerges with the hook but is stopped by "Tony." The masked person is revealed to be Aunt Harriet, who explains that Simon has been driven insane by guilt over Tony's death. The ritual calms Simon by allowing him to pretend that his brother is still alive. He plays a recording of Tony singing, Simon plays the organ, and Harriet is a masked "singer" and plays Tony's part.

Eleanor falls in love with "Tony" and is conflicted by her seemingly-incestuous thoughts. She is about to commit suicide, but he stops her and confesses that he is not her brother. Meanwhile, Simon had an affair with Eleanor's nurse, who guesses Simon's murder attempt and so tries to leave. When he stops her, she threatens to expose him, which makes him drown her in the garden pond. Simon tells Eleanor that the nurse left.

The fake Tony investigates the chapel and finds the real Tony's mummified body, despite Harriet's attempt to stop him, after the struggle reveals a hidden wall. He is about to leave but is stopped by Simon, who admits he had tricked the real Tony into writing the suicide note and then murdered him and that he had sabotaged the car. Simon slugs and binds him.

When the fake Tony comes to his senses, Simon plays the organ with the real Tony's body now seated on a chair. Simon informs the impostor that he and Tony had a talk and have decided to have the impostor "join" Tony.

Harriet appears and persuades Simon to leave since she will take care of the situation. She is unfazed at seeing the corpse and so evidently knew the truth as well. She sets the chapel on fire with a lantern to protect Simon and then leaves. Eleanor, alarmed by the fire, appears. She sees the real Tony's body and unties the fake Tony.

They flee the chapel, and since it is ablaze and Tony's body is inside, Simon's madness overwhelms him. He staggers to the chapel to try to "rescue" Tony but is trapped by the flames and is overcome as he clutches Tony's skeletal remains.

The impostor is exposed after discovering the real Tony's body, and Simon's guilt and insanity are revealed, culminating in violent confrontation within the mansion.

The ending brings the Ashby family's secrets into the light, with the impostor's deception unraveled and Simon's descent into madness exposed. The twisted inheritance plot and psychological manipulation reach their breaking point, leaving the survivors to reckon with the consequences. The film closes the loop on its themes of identity, guilt, and the destructive power of family dysfunction.