A manned space flight from Venus crash lands in the Mediterranean, losing its most precious cargo: reptilian eggs from the planet's surface. They come into the possession of an Italian zoologist (Frank Puglia), who watches as one hatches to reveal a rapidly-growing monster. His American granddaughter, Marisa (Joan Taylor), and returned astronaut Calder (William Hopper) must battle with the American and Italian military to corral the creature before it destroys everything in its path.