A gripping World War II mystery novel with a cryptographic twist, Enigma's hero is Tom Jericho, a brilliant British mathematician working as a member of the team struggling to crack the Nazi Enigma code. Jericho's own struggles include nerve-wracking mental labour, the mysterious disappearance of a former girlfriend, the suspicions of his coworkers within the paranoid high-security project, and the certainty that someone close to him, perhaps the missing girl, is a Nazi spy. The plot is pure fiction but the historical background, Alan Turing's famous wartime computing project that cracked the German U-boat communications code, is real and accurately portrayed.