Night Monster

Three doctors who were trying to cure Kurt Ingston's paralysis are invited to his secluded swamp-side mansion. They are welcomed by the household, which includes the stern butler Rolf and the other staff, as well as Ingston's enigmatic sister Margaret. Their arrival marks the beginning of a tense stay as rumors of murder swarm around the estate.

Dr. Lynne Harper, a lady psychiatrist, is secretly summoned by Margaret to prove she is not insane. She is accompanied by her neighbor, mystery writer Dick Baldwin, who rescued her after a car breakdown in the swamp. Neither Ingston nor Miss Judd welcomes her presence, but she is kept overnight.

During dinner, Ingston makes it clear that he believes the three doctors caused his current condition. The confession heightens the sense of danger and distrust among the guests. The tension is thick as the others exchange wary glances.

The party witnesses Agar Singh's uncanny display of materializing a Sicilian skeleton. The demonstration deepens the sense that supernatural powers might be involved. The others are left unsettled by this spectacle.

Lynne Harper is forbidden to meet Margaret, highlighting a forbidden dynamic within the household. This restriction underlines the controlling atmosphere surrounding the estate. The prohibition contributes to growing unease.

One by one, the three doctors are frightfully killed as they prepare for bed. The deaths plunge the house into panic and suspicion, leaving everyone guessing who will be next. The sense of danger becomes inescapable.

Dick Baldwin and Police Captain Beggs confront Ingston in his room and demand answers. They discover he is not paralyzed after all, but a triple amputee who can fake mobility. The revelation shifts the focus of the investigation to Ingston as the killer.

Suspicion quickly falls on Laurie, the chauffeur who was last seen driving a murdered ex-employee back to town. He is found dead, removing another potential suspect from the equation. The investigation tightens around the remaining residents.

Dick confronts the killer outside the estate and learns that Ingston learned to materialize arms and legs through his studies with Agar Singh. The confrontation confirms Ingston as the culprit and sets up the final confrontation.

Margaret sets fire to the unholy house, committing suicide while taking Miss Judd with her. The mansion erupts into flames, spreading chaos and smoke through the halls. The collapse of the estate marks the turning point toward the finale.

As the house burns, Agar Singh shoots Ingston, ending his reign of terror. Dick and Lynne are saved by Singh's intervention amid the blaze. The estate burns to the ground as the killer dies.

In the aftermath, Dick and Lynne survive and the swamp town begins to recover from the terror. The mystery is laid to rest, albeit with more questions than answers about the uncanny events. The film closes on a somber note as the flames die down.