When a lifeboat crew discovers a luxury cruiser adrift in the English Channel, they find on board are a group of wealthy pop stars and their girlfriends, one of whom is dead. Doomwatch investigate, and discover that the death was not from drug abuse as was previously suspected; instead they begin to uncover the facts behind the dumping of a deadly chemical warfare compound in a deep sea trench, which seems to be far from dormant.

The Doomwatch team investigate the mysterious outbreak of a deadly subtropical disease which somehow has cropped up on an isolated island off the coast of the UK.