 During the Second World War, a team of genius is put together near to London to study means of breaking the German code used in the communication. Tom Jericho broke this code in the past and had a break-down. Now his passion Claire Romilly is missing and the British counter-espionage system believes she is a German spy. Tom becomes closer the Claire s best girl-friend Hester Wallace and together they try to resolve the mystery of the disappearance of Claire in an war environment surrounded by suspicion and stress.