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During WWII, men and women working at Bletchley Park played a vital role, breaking the codes used by the German military. Nine years later, former codebreaker Susan is a housewife and mother, but she continues to recognize patterns that surround her in everyday life. When a series of women are brutally murdered around London, Susan sees a pattern emerging. However, when a police-search for what Susan believes to be an overlooked victim turns up nothing, she realizes she cannot solve this puzzle alone. Enlisting three former Bletchley Park colleagues: Millie, Lucy, and Jean; Susan knows they have little time to break this code before the killer strikes again.
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Episode 1
Sun, Apr 13, 201446 mins
During the war Alice Merren was one of Bletchley's brightest code-breakers. Now it is 1953. Lucy has a clerical job for Scotland Yard, Millie works as a German translator and Susan a housewife perturbed that her husband's promotion may take them overseas. Jean visits Alice in prison, awaiting trial for killing her old flame and Bletchley colleague John Richards. Jean is convinced of Alice's innocence and persuades her friends to investigate. They discover that John sent flowers to a young girl, Lizzie Lancaster and a search of her flat reveals she is in possession of a classified military file and a press cutting of an incident where military personnel were injured by a chemical experiment on Salisbury Plain. The women save Lizzie from a hit and run and Jean correctly assumes that she is Alice's daughter. The Bletchley circle believe both mother and daughter have been set up by John's killer who was also responsible for the Salisbury Plain incident.
