Five teenagers on a boating trip discover a mysterious ship and decide to board it and investigate. Inside they find scientific equipment and a man in a state of shock.
Then their dinghy sinks in a flash storm and they are stranded on the ship. Curious, they try to find out what has taken place - but then horrific things begin to happen to them. Dorothy vomits strange, small creatures, Margaret is bitten in the neck by a fish, Bob and Julie taste some powder and transform into hideous monsters.
Mike eventually comes up with the answer - radioactive waste contamination from the abyss - but can he survive the terror and get to safety?