Young graduate Ruth Gilmartin is shocked when her mother Sally reveals details of her early life as Russian emigre Eva Delectorskaya, recruited by the British Secret Service during the Second World War. Although nearly 40 years have elapsed since then, the former agent believes that missions undertaken during the conflict on behalf of her spymaster - and lover - Lucas Romer have served to place her life in danger.

Eva's 1941 mission to the US, where she seduced a Washington DC official attached to President Roosevelt's office before surviving an attempt on her life in New Mexico, could hold the key to her present difficulties. Ruth poses as a journalist to meet Lord Romer, and although his suspicions are aroused, he appears unaware when Eva follows him to his Chelsea house.