Beneath the streets of London lie many secrets. Subterranean rivers carve channels through darkened caverns. Hidden laboratories and government offices from WWII offer a maze of corridors and abandoned medical experiments. Lost in the depths of this underground are the contents of a looted Spanish galleon from the days of Henry VIII and a Nazi V-2 rocket that contains the most horrible secret of all. Carmen Kingsley, in charge of London projects for the British Museum, and Scotland Yard Inspector Sherwood Peets race to unravel the mysteries behind these contents before the great city succumbs to a frightening disease not seen since the age of the Henrys - the English Sweat. It all comes to a climax beneath London with the discovery of a horrifying species of genetically altered "super rats" that threaten to invade London and the British Isles.