After a new cannery introduces scientifically augmented salmon to a seaside town in the Pacific Northwest, a species of mysterious, mutated sea creatures begin killing the men and raping the women.

Warren Stacy, an office equipment repairman, begins murdering women after they reject his advances. To minimize the evidence, Stacy always kills while naked, wearing nothing but gloves, and further evades the law with his strong alibis. Veteran detective Leo Kessler is convinced of Stacy's guilt and begins using questionable methods to catch him.