Paul Toombes [Vincent Price] is a renowned horror star whose signature role is Dr. Death, a skull-faced serial killer that has become his calling card. At a Hollywood party celebrating his fifth Dr. Death film, Paul announces his engagement to Ellen Mason, who gifts him an engraved watch as a personal keepsake. The mood shifts when Oliver Quayle [Robert Quarry] reveals to Paul that Ellen had previously worked in his movies and had slept with him. Troubled and angry, Paul’s reaction unsettles Ellen, who heads back to her room, only for a masked Dr. Death-costumed figure to confront her with a knife. Moments later, an apologetic Paul enters the room, and Ellen’s head drops from her shoulders the moment he touches her. Although Paul is acquitted, he remains unsure whether he himself was the killer, and his career collapses as he spends years in a mental hospital.
Twelve years pass, and Paul is summoned to London by his friend Herbert Flay [Peter Cushing], a screenwriter who has teamed with Quayle to produce a Dr. Death television series for the BBC. During a sea voyage to England, a determined young actress, Elizabeth Peters [Linda Hayden], steals his watch and doggedly tracks him through London to Flay’s house. In Flay’s spider-infested basement, Paul encounters Faye Carstairs [Adrienne Corri], Flay’s wife and a former Dr. Death co-star who was driven to madness after a car crash. Outside, Elizabeth spots the costumed figure prowling the grounds; she misidentifies it as Paul and approaches, only to be killed with a pitchfork. When her body is found, Scotland Yard suspects Paul, since the murders mirror Dr. Death scenes.
Displeased that Quayle has given Dr. Death a female “assistant” for the series—something the films never had—Paul berates his co-star on set; she is soon found hanged by her hair, another echo of Dr. Death. Scotland Yard questions Paul again but finds no conclusive evidence. Paul endures pressure from Elizabeth’s parents, who recover the stolen watch and threaten to hand it over to the police unless a ransom is paid. The killer, however, lures the parents into the house and impales them both with a broadsword. On set, the director is crushed by a descending bed canopy in a trap meant for Paul. Later, Paul is chased through the studio by the killer as he heads for an interview.
Julia Wilson [Natasha Pyne], Quayle’s public relations chief, discovers a contract in his files but is murdered by the killer; Paul discovers her body in a recreation of Ellen’s death, seated before her dressing table. A distraught Paul carries her body to the set, switches on the camera, and sets the place ablaze. Believing Paul has perished in the fire, Flay signs a contract to take over as Dr. Death. Later he watches the reel of Paul’s supposed death, only to see Paul seem to walk out of the screen, burned but alive. When Paul asks why Flay wants to destroy him, Flay admits he wrote the Dr. Death role for himself but was passed over in favor of Paul; he murdered Ellen to ruin Paul’s career but was still denied the role. He then reveals that Julia’s contract stipulated that if Paul died, Flay would inherit the Dr. Death role by right. The two struggle into the basement, where Faye Carstairs enters and stabs Flay in the back. Flay falls into a tank of spiders and is devoured.
Paul applies makeup to his burn-scarred face, now resembling Flay, and sits down to dinner with Faye. She quips that his upcoming meal will be his favorites—sour cream and “red herrings”—and they share a dark, conspiratorial laugh.
