Henry likes to kill people, in different ways each time. Henry shares an apartment with Otis. When Otis' sister comes to stay, we see both sides of Henry: "the guy next door" and the serial killer.

American astronaut Frank Douglas mysteriously disappears from his spacecraft as it parachutes to Earth. He is apparently replaced by or turned into a large, radioactive, humanoid monster. A team of scientists and military men attempt to capture the monster.