June 8, 1954. Several English nationals have defected to the USSR, while a witch hunt for homosexuals rages across Britain. In these circumstances, no one is surprised when a mathematician by the name of Alan Turing is found dead in his home in the sleepy suburb of Wilmslow. It is widely assumed that he has committed suicide, unable to cope with the humiliation of a criminal conviction for gross indecency. But a young detective constable, Leonard Corell, who once dreamed of a career in higher mathematics, suspects greater forces are involved.
In the face of opposition from his superiors, he begins to assemble the pieces of a puzzle that lead him to one of the most closely guarded secrets of the war: the Bletchley Park operation to crack the Nazis’ Enigma encryption code. Stumbling across evidence of Turing’s genius, and sensing an escape from a narrow life, Corell begins to dig deeper. But in the paranoid, febrile atmosphere of the Cold War, loose cannons cannot be tolerated and Corell soon realizes he has much to learn about the dangers of forbidden knowledge.
He is also about to be rocked by two startling developments in his own life, one of which will find him targeted as a threat to national security.