An other-worldly story, set against the backdrop of Cold War era America circa 1962, where a mute janitor working at a lab falls in love with an amphibious man being held captive there and devises a plan to help him escape.

People living at a seashore town are frightened by reports of an unknown creature called "the sea devil". Nobody knows what it is, but it's really the son of doctor Salvator. The doctor performed surgery on his son and now young Ichtiander can live under water. This gives him certain advantages, but also creates a lot of problems.