The Bletchley Circle

Former Bletchley Park colleague Alice Merren is awaiting trial for murder. Despite the overwhelming evidence of Alice's guilt, Jean is determined to prove Alice's innocence.

The circle's investigation uncovers three men with chemical burns in a truck crash in Salisbury plain and the team suspects a high level cover-up involving the Alice's trial.

Millie helps Alice get a job, but when she suddenly disappears and the police won't help, the women take the investigation into their own hands.

From PBS - The women realize there's corruption in the vice squad and decide to intercept the crime ring themselves.