An American space mission to Venus brings back a bizarre reptilian creature from the planet's surface, but once exposed to Earth's atmosphere it suddenly begins to grow at an alarming rate and wreaks havoc through the streets of Rome. Sci-fi thriller, starring William Hopper, Joan Taylor and Frank Puglia.

When the first manned flight to Venus returns to Earth, the rocket crash-lands in the Mediterranean near a small Italian fishing village. The locals manage to save one of the astronauts Colonel Calder, the mission commander. A young boy also recovers what turns out to be a specimen of an alien creature. Growing at a fantastic rate, it manages to escape and eventually threatens the city of Rome.