The Bletchley Circle: San Francisco

Millie Harcourt and Jean McBrian travel to San Francisco and join forces with two American codebreakers - Iris Bearden and Hailey Yarner - to pursue a serial killer from their war days, who has resurfaced in the United States.

Millie, Jean, Iris, and Hailey continue their complex investigation that has spanned two continents, but can they crack the codes before the killer hits close to home?

Our four women delve into the mysterious death of Iris's suburban friend, uncovering a complex cluster of marriages built on lies and deception. In her quest to forge a new life, Millie must confront a long-lost cousin, who may hold the key to a future in San Francisco.

After a seemingly innocent man is charged with murder, the women become enmeshed in a tangled suburban tragedy, racing to find both the true killer and the methods before the scent goes cold. Jean meanwhile grapples with how - and where - to build a new life for herself.

A bloodied and battered stranger collapses on Millie and Jean's doorstep, dragging them into a mysterious criminal underworld. In a race against time, the four women must unravel the patterns behind a series of attacks in order to avoid becoming the next victims.

Having uncovered a covert system of police corruption, the women must go it alone, crafting a complex sting operation in order to draw out two warring factions and see justice done. Time is precious, as their investigations have triggered deportation proceedings that could soon send Jean and Millie back to the UK.

When a Russian diplomat dies in Iris's arms, the FBI sweep in to control the story and rule the death accidental. Iris is forced to get involved to protect her family. Hailey meanwhile befriends a world-renowned visiting cellist, and all four soon find themselves embroiled in a dangerous international firestorm.

A death in the Big Bop Club brings an international incident right to their doorstep, while the women grapple with Jean's sudden disappearance. Reeling from betrayals, Iris and Hailey work with Millie to plan a daring undercover operation to find Jean and expose Cold War treachery.

For the first time, the curtain is being pulled back on the making of Bletchley Circle: San Francisco. The people, the set, the music, the filming, the costumes, this special episode offers a secret pass into the Inner Circle. Codes will be deciphered.