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.

Autumn, 1948: Iris Digby, her American diplomat husband Sasha, and their two children vanish from London. 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? Four years later Ruth Macallister receives a postcard from Iris, the twin sister she hasn't seen since their catastrophic parting in Rome in the summer of 1940. Now Ruth is on her way to Moscow, posing as the wife of counterintelligence agent Sumner Fox in a precarious plot to extract the Digbys from behind the Iron Curtain. -- adapted from jacket