The Bletchley Circle: San Francisco premieres

Set during the thrilling social change of the mid-1950s, The Bletchley Circle: San Francisco captures the lives of four remarkable women gifted with extraordinary intelligence, breathtaking capacity for pattern recognition, and a genius for decryption.

This new sequel revisits two of the original foursome, Millie and Jean, 14 years on. They’re on the trail of a serial killer who leaves mysterious square symbols on his victims’ palms. Chillingly, one of their colleagues was murdered in the same way during the Second World War.

Suspecting a US soldier is behind the crimes, Millie and Jean travel to San Francisco. There they team up with new pals Iris and Hailey, who spent the war cracking codes for the American intelligence service. In the process, the four women are plunged into fascinating corners of the city, forge powerful relationships, and rediscover their own powers and potential.

Wednesdays on ITV.