Anna Maxwell Martin

Four women who worked as codebreakers at Bletchley Park have taken up civilian lives. Susan has collated data about a series of murders. She tries to convince the police she knows where another body is, but they are unable to locate it and dismiss her. She turns to her three friends and they work out where the next victim will be taken, find the body, and then decide they are the only ones who can track down the killer.

When Sarah Burton returns to her hometown as headmistress, she is full of ambition, determined to create a great school and to inspire her girls to take all they can from life. But in the aftermath of the First World War, the country is in depression and ideals are hard won. Lydia Holly, the scholarship girl from the shacks, is the most brilliant student Sarah has ever taught, but when her mother's health fails, her education must be sacrificed -...

It's 1939 and Europe teeters on the brink of war. Ten strangers are invited to Indian Island, an isolated rock near the Devon coast in southern England. Cut off from the mainland, with their generous hosts Mr and Mrs U.N. Owen mysteriously absent, they are each accused of a terrible crime. As each member of the party starts to die one by one, the survivors realize that one of them is a killer and start to turn on each other.