An inexplicable wave of murders has the country gripped with terror. Ordinary men and women are suddenly going mad, committing brutal and horrific killings before slaying themselves in equally gruesome ways. General Charles Kirk of British Foreign Intelligence thinks the case has something to do with the most evil man he has ever encountered: Tommy Ryde, a British spy who defected to the Nazis during the Second World War and who seemed to possess a strange hypnotic power. But Ryde has been dead for forty years - or has he? Kirk and his colleague Bill Easter are determined to find out. The trail takes them first to Berlin to seek answers from a notorious Nazi war criminal, then to an underwater search of a sunken U-boat off the Scottish coast, and finally to the torture chambers beneath a madman's Gothic castle in Dartmoor, where they will come face to face with the living incarnation of evil ...