Scientist Alex Marsh has developed a powerful paralytic-hypnotic nerve gas for military use, testing it on sheep deep in the Mojave Desert with a mix of scientific awe and moral certainty. He believes that forcing enemies into a trance could save lives by ending battles without killing anyone. The project draws in his mentor, Dr. Frederick Ramsey, and brings into the orbit his partner, Tom Holland, along with Alex’s girlfriend Carol Wilson. Despite Carol’s warnings about the danger and ethical murk, Alex is resolved to keep pushing forward until war casualties are a thing of the past.
A local mailman stumbles into the test site and is overcome by the gas, yet he survives the encounter. Buoyed by this near-miracle, Alex rushes to Ramsey’s home to reveal his progress, hoping a swift antidote or refinement will come next. The plan hinges on the idea that those exposed to the gas can be kept in a controlled trance for a defined period, making them malleable to commands and potentially preventing deaths in future conflicts. Carol remains uneasy, while Tom offers cautious support, sensing both possibility and peril in the breakthrough.
In the lab, disaster strikes: a liquefied version of the gas spills, and in a panic to clean it up, Alex touches the liquid and contracts the condition himself. He wakes to find his hands and extremities darkened and painful, a visible sign of the transformation to come. When his lab assistant, Carlos, reaches out, Carlos withers away and dies. Frantic, Alex sets the lab ablaze to cover the tragedy and escapes. A gas-station attendant dies after briefly touching him, forcing Alex to flee once more.
At Ramsey’s house, Ramsey agrees to seek an antidote with help from Tom, but the initial cure proves ineffective. Desperate, Alex drinks a vial from the serum Ramsey was developing, hoping for a cure. Instead, the serum mutates him further, swelling and darkening his already altered form until he becomes nearly unrecognizable. Overwhelmed by horror at his own appearance, he accidentally kills Ramsey and staggers away, trying to conceal the mutation with a trench coat and a fedora.
Seeking shelter, he hails a cab, but his muffled speech is indecipherable to the driver. When the driver reaches for him to exit the vehicle, he is killed after contact with the mutated prodigy, and Alex escapes into the night. He later collapses on a remote beach, slipping into a fitful sleep as a curious little boy—Davey—plays nearby on the rocks and nearly stumbles upon the hidden, altered man.
The mutated scientist shuffles toward Tom’s house where Carol is staying. He breaks in and, unable to form words, can only scrawl a single plea on paper: “TOM SERUM HELP.” The police close in, and Alex finds himself cornered on the shore with armed officers surrounding him. Carol pleads for his surrender, but the creature that was once a man lunges forward, and in the final struggle, is gunned down in the surf, bringing a grim end to a project that promised a humane path to warfare but delivered a nightmare of its own making.
