julie graham and rachel stirling lead the cast in this drama about a team of female world war ii code breakers'. '.strtoupper('t')he spin off series is set three years after the last bletchley circle series'. '.strtoupper('t')he series is set in the 1950s during the aftermath of world war two and follows the female codebreakers who travel to san francisco to solve a murder investigation that may explain the death of their colleague during the war'. '.strtoupper('t')hey are joined by us code breakers iris  and hailey, who – like their british counter parts – feel undervalued, under appreciated and cast away after the war'. '.strtoupper('t')he women face adversity, both in the face of the perpetrators of the crimes, and from the patriarchal 1950s society they work in'. '.strtoupper('r')elease date  20th may 2019