In World War II they were code-breakers at Bletchley Park; brilliant, invaluable members of an elite team whose task was to crack German intelligence. Their success was their downfall. Seven years after helping to win the war they are housewives, mothers, girlfriends, shadows. Bound to the Official Secrets Act, their part in the Allied victory cannot be told; their finest abilities covered in dust sheets of security never to be seen again - unless... Susan has been reading newspapers, listening to the radio, following news of a serial killer targeting young women. She believes she can flesh out the pattern that will reveal his identity, but she can't do it alone. Calling on her companions from Bletchley, she persuades them to join her. But can yesterday's code breakers become today's detectives? All it will take is following the trail, breaking the code - and possibly risking their lives.