In Kate Quinn’s latest, three young women – a glittering society deb, an all-business super-secretary, and a mousy homebody – become friends when tapped to help in the massive World War II codebreaking effort at Bletchley Park. The excitement and tension of the work are palpable, and Quinn makes the women’s lives full and interesting. Thanks to extreme compartmentalisation and the Official Secrets Act, they can’t be sure what one another are working on, but after the War, with time to reflect, there are hints a Soviet spy had lurked among them. Most convinced of this is Beth, confined to a mental hospital, and who will believe her?