Geneticist Peter Houseman, a professor at a private university, leads a pioneering program in DNA research with the help of his friend Mike and his young collaborator Willy. He aims to create a serum that could prevent aging and defeat death, a dream that keeps him pushing forward even as a skeptical funding commission raises questions about his ongoing requests. Among the panel’s voices are an aging Professor Lloyd, who resents Peter’s progress, and Inspector Sally, with whom Peter soon develops an uneasy attraction. To keep the project afloat, the team leans on the technical guidance of Dr. Elliot Stein, [Allen Lewis Rickman], who helps oversee the experimental protocol and the modified DNA at the core of the serum. Despite the scrutiny, Peter decides to test the serum on himself, hoping the results will vindicate his work.
Initially, the experiment appears to yield positive results: Peter feels stronger, his vitality returning in surprising ways, and he begins a tentative relationship with Sally even as her son Tommy watches with suspicion. Yet as days pass, Peter’s behavior grows increasingly erratic. He slips into a nightclub where he brutally harms a prostitute, an act he cannot fully explain or remember. Soon after, Patricia, a flirtatious student who had tried to seduce him, is raped and strangled, a brutal sequence that unsettles everyone around him. Complicating matters, Peter’s own body begins to change, taking on reptilian traits and signaling a deeper physical transformation.
A car accident by a police vehicle leaves Peter hospitalized, where he experiences a rapid and disturbing aging process that saps his strength. He asserts that the serum has granted him a form of immortality—he will forever remain what he has become. In the hospital, Dr. Michael Foster, [George Gerard], and the other investigators watch as Peter’s body regresses beyond normal bounds. Dr. Lloyd’s theory grows darker: Peter’s form seems to be sliding back to an earlier point in human evolution. As Peter grows more monstrous, he escapes the hospital, killing Lloyd and Willy, and discovers that his altered frame now requires human blood to sustain itself. He kidnaps Tommy and returns to the university lab, leaving a bloody trail in his wake as he seeks one final chance to fix the experiment.
Tommy finally breaks the serum bottle, and mother and son flee through the campus while Peter, now a terrifying anthropomorphic creature, gives chase. Mike and the police close in, awaiting outside, and Sally, Tommy, and the others move to safety. Peter is confronted at the door, shot by the authorities, and begins to decompose right after his lethal confrontation with the law.
In the aftermath, Tommy quietly reveals to his mother a mysterious lizard kept in a box. When Sally urges him to let it out or risk its death, Tommy simply says it will never die, hinting that a fragment of Peter’s legacy has survived in a new, enduring form. The ending leaves a haunting sense that the pursuit of youth and life has a dangerous, inescapable cost, with a creature of science lingering beyond the boundaries of death.
