Former Bletchley Park worker Alice Merren is in prison awaiting trial for the cuddle of the eminent scientist John Richards. Driven by her belief in Alice's innocence and that she is hiding the truth about John's passing, Jean attempts to regroup the circle in order to help establish the innocence of one of their own.

Following the discovery of Lizzie Lancaster's true identity, the women face a race against time to prove Alice's innocence and save her from the hangman's noose. However, subsequent investigations lead to the discovery of a much darker military conspiracy.

Millie introduces Alice to her new business and her associate Jasper. Alice is worried but Millie assures her it's all fine and just a little way of earning some money until she can get some more translating work. Millie ends up being kidnapped and taken to a seedy Hotel by some Soho gangster types. Alice turns to Jean and Lucy to try and help her.

The girls inform the police tabout Jasper's cuddle and the next morning Ben informs Lucy that the tip off was wrong, there was no dead body and somebody managed to get there first. The girls conclude that there must be corruption in the vice squad so and they decide that catching them red handed is the only option.