Seven years after WWII, four women who worked as codebreakers at Bletchley Park have taken up mundane civilian lives. Susan, now a housewife, has co
llated data about a series of murders. She tells the police she knows where another body is, but they are unable to locate it and dismiss her. Susan turns to her friends Millie, Lucy, and Jean, former codebreaking colleagues at Bletchely Park. They work out where the next victim will be taken, find the body, then decide only they can find the killer.