Two former members of England's secret WWII code-breaking team head to San Francisco, where two women have been murdered in circumstances identical to earlier London crimes. Jean McBrian (Julie Graham, Shetland) and Millie Harcourt (Rachael Sterling, The Young Victoria) team up with American code-breakers as they face local corruption and cold war treachery in an effort to bring an elusive killer to justice. 8 episodes, 6 hrs, 1 DVD.