The sleepy fishing port of Skullen Bay on the SE Coast of England is suddenly plunged into a terrifying nightmare as several locals vanish without trace. The only witness to the disappearances is the town drunk who rambles on to anyone who will listen about sea monsters. A local reporter and press photographer hire a boat to try and capture evidence of the creature. When the wreckage of their craft is found the police manage to salvage the film from the camera which, when developed, reveals shocking close-ups of something unspeakable. As the body count continues to rise the local police appear helpless to prevent more slaughter. In sheer desperation, the mayor's office brings in an expert in marine biology who launches an expedition to try and capture the creature. An expedition which will uncover a terror beyond imagination.