Doctor X

Daily World reporter Lee Taylor investigates a string of nocturnal, cannibalistic murders in New York City. Witnesses describe a horribly disfigured 'monster' behind the killings, and the victims are found with evidence of cannibalism. The murders consistently occur at night under a full moon.

The police call in Dr. Xavier for his medical opinion, but their real motive is to probe his medical academy, where the brain scalpel used in the killings is exclusive. Xavier is asked to help identify the killer using his methods, while his institution becomes a potential target.

The police outline the main suspects: Wells, an amputee who studies cannibalism; Haines, who displays voyeuristic tendencies; Duke, a grouchy paralytic; and Rowitz, who researches the psychological effects of the moon. Each man has a potential motive and a unique vulnerability that makes the case complex. The list of suspects sets up the dramatic tension for the ensuing tests.

The police impose a 48-hour deadline for Xavier to capture the killer in his own way. Reporter Taylor continues his investigation and meets Joanne Xavier, the doctor's icy daughter, who resents his role in derailing her father’s earlier lead.

Xavier arranges an unorthodox experiment at his beach-side estate, intending to expose the killer with live heart-rate monitors attached to each suspect. A re-enactment of a murder is carried out by Xavier's loyal servant Otto and his maid Mamie, while Wells is excluded because he has only one usable hand. The participants are seated and the doors are sealed to monitor true physiological responses.

A blackout obscures the proceedings, and when power returns the room finds Rowitz dead from a scalpel to the brain. The body later appears cannibalized, confirming the killer's gruesome methods remain active.

On the following night, Xavier orders another murder reenactment. Mamie is frightened, so Joanne steps in to act the part while Wells remains excluded from the seating as the others are handcuffed. The setup keeps Wells at the recording cabinet to prevent interaction.

Wells secretly enters a forbidden laboratory and uses synthetic flesh to transform into the Moon Killer. He murders Otto, then reveals that his killings have been a long-running project to harvest living flesh for his experiments and that he intends to claim Joanne as his final victim.

Taylor, concealed among wax figures of the victims, leaps Wells during the confrontation. He hurls a kerosene lamp, setting Wells on fire, who crashes through a window and tumbles off a cliff into the ocean below.

Taylor reports the sensational story to his editor, suggesting space in the marriage section for Joanne and himself. The investigation resolves with Wells defeated and the killer unmasked, while Joanne's relationship with Taylor hints at a hopeful future.