In the autumn of 1948, Iris Digby vanishes from her London home with her American diplomat husband and their two children. The world is shocked by the family's sensational disappearance. Were they eliminated by the Soviet intelligence service? Or have the Digbys defected to Moscow with a trove of the West's most vital secrets?

To save her sister, who, along with her American diplomat husband and children, is trapped behind the Iron Curtain, Ruth Macallister embarks on a dangerous mission, and as the sisters race toward safety, a dogged Soviet agent forces them to make a heartbreaking choice.