The Bletchley Circle

Set in 1952, following four women whose work at Bletchley Park during WWII helped break codes used by the German military. Susan, Millie, Jean and Lucy have returned to their normal lives, but when Susan identifies a hidden pattern in a series of murders, she enlists the help of her former colleagues to crack the case.

The women close in on the killer of the five girls, narrowing their list of suspects down to three. However, a shocking discovery forces them to change their theories and they set a trap to catch the culprit using Lucy as bait - but the operation goes horribly wrong.

Susan and her code-breaking allies seem to have finally tracked down the murderer, and attempt to confront him. As the women get closer to their target, they are forced to put themselves in grave danger.