'Top-class' The Times

March 1943, the war hangs in the balance, and at Bletchley Park Tom Jericho, a brilliant young codebreaker, is facing a double nightmare. The Germans have unaccountably changed their U-boat Enigma code, threatening a massive Allied defeat. And as suspicion grows that there may be a spy inside Bletchley, Jericho's girlfriend, the beautiful and mysterious Claire Romilly, suddenly disappears.

'A compulsive page turner' Daily Mail
'As human, intelligent and gripping as documentary fiction can get' Financial Times