Capt. Thorne Sherman lands his ship on an isolated island to make a delivery, only to find that mad doctor Marlowe Craigis is experimenting on shrews in an attempt to shrink them. The opposite happens, and the shrews become enormous and hungry for human flesh, leaving everyone on the island in peril, including the doctor's pretty daughter, Ann, and her unappealing fiancé, Jerry. Then, Thorne tries to organize an escape plan.