A mysterious, man-sized monster kills a fisherman at sea. Biologist Ted Baxter (Kent Taylor) finds the body on the beach, along with Federal Agent William Grant (Rodney Bell), and they decide to investigate the death. Ted eventually discovers that Dr. King (Michael Whalen), another marine biologist, created the monster and the radioactive rock with a mutating device in his laboratory. Meanwhile, foreign agents try to discover Dr. King's secrets, while Ted and King's daughter (Cathy Downs) develop a relationship.