| Director | Gordon Hessler |
|---|---|
| Budget | $350,000 |
| Box office | $1.2 million |
The movie's structure is fragmented, as it alternates between three plot threads.
A man jogging through urban London grabs his heart and collapses. He wakes up in a hospital bed. The nurse tending him gives him water and leaves. He pulls down the bed covers to discover that his lower right leg has been amputated. He screams. Later scenes repeat the same action as his other limbs are amputated.
Elsewhere, intelligence operative Konratz returns to his home country, an unidentified Eastern European totalitarian state. After being debriefed by Captain Schweitz, Konratz steps around the table and places a hand on Schweitz's shoulder, paralysing and then killing him. Konratz is later reprimanded by his superior Major Benedek for his torturing an escapee, Erika. Konratz kills Major Benedek in the same way.
In London, Metropolitan Police Detective Superintendent Bellaver investigates the rape and murder of a young woman, Eileen Stevens. Bellaver goes with young forensic pathologist Dr. David Sorel to the clinic of her employer Dr. Browning but he provides no useful information. A young woman, Sylvia, is picked up at the Busted Pot Disco by the sinister Keith. She is killed by Keith and her body is later found drained of blood.
The two young women have apparently been raped and murdered by the same individual. Bellaver sends out several young policewomen to try to entrap the killer. WPC Helen Bradford, wearing a wire and electronic tracer, goes to the same club where she lets herself get picked up and driven away by Keith. The police follow and arrive just after Keith has attacked her and appears to be drinking blood from her wrist. With apparent superhuman strength, Keith fights off the arresting police and drives off. A long chase ensues by car and on foot through suburban London, during which Keith tears off his hand whilst handcuffed to the bumper of a police car in an attempt to escape. The pursuit ends at an estate where Keith throws himself into a vat of acid in an outbuilding. The building turns out to belong to Dr. Browning, who explains that he uses the acid to destroy possible pathogens in his biological experiments. Bellaver is ordered to stop his investigations but Sorel decides to continue on his own. Accompanied by WPC Bradford, he goes to Browning's laboratory. Bradford and their car disappear. Bradford wakes up restrained in the same hospital bed with the same nurse attending her as the dismembered jogger.
The narrative strands begin to come together when a senior UK Government officer, Fremont, meets Konratz at London's Trafalgar Square, and agrees to turn over all the evidence in exchange for a captured pilot. Soon after, Konratz goes to police headquarters to remove all the evidence, and kills Bellaver.
Back at the laboratory, Sorel discovers Browning is about to dismember Bradford, as part of a plot to replace humans with composite beings. As they struggle, Browning reveals himself to be one of the composite superhumans. Konratz appears and is angry that Browning's actions have interfered with his part of the plot. When Browning expresses misgivings, he and Konratz struggle, allowing the others to escape. Konratz is pushed into a vat of acid in the laboratory room. As Sorel and Bradford get outside, Fremont appears and tells them to wait for him. He goes back in and, in talking with Browning, reveals himself as a composite. He then subdues Browning and pushes him into the acid. Fremont leaves with Sorel and WPC Bradford. When Sorel asks if it is all over, Fremont tells him it is only just beginning.