"I can tell you something about this place. The boys around here call it The Black Lagoon. Only they say nobody has ever come back alive to prove it."
Something lurks under the waters of the Black Lagoon – a prehistoric monster, a creature that existed before the dawn of man. This "missing link", a cross between the land-living and the sea-living is the target of an expedition bent on capturing it and bringing it back to civilization for study. The scientists drug and capture the creature, who becomes enamored with the expedition’s female scientist (Julia Adams). The lonely creatures escapes, and kidnaps the object of his affection. A rescue mission is mounted and the small group sets out to rescue the kidnapped woman and send the creature back to the murky depths from which it emerged.