Susan Murphy, an ordinary California girl transforms into a giant after she is struck by a meteorite on her wedding day. The government immediately take her away to a secret base and lock together with other monsters: Dr, Cockroach, a genius doctor of science with a head of an insect; a brutal fishman named the Missing Link, jelly-like and unkillable B.O.B and a hundred-meter tall Insectosaurus. However, their imprisonment didn’t last long. An alien robot attacks the Earth, and the president sends the monster squad to save the planet from imminent destruction.