When an old man strikes up a conversation with her on the steps of St Paul's in London, and attempts to tell her the story of a murder that has not been brought to justice, journalist Kate Murray brushes him aside - until he mentions her beloved grandmother. Before she can reply, he walks away and she watches in horror as he is knocked down on the road and killed. That fateful moment unleashes a whirlwind of events that takes Kate back into her grandmother's war-time past and across the Atlantic, but every step she takes is tracked by an unknown and deadly enemy...