As the Blitz continues to ravage London, Ellie McDonnell is approached by British Intelligence officer Major Ramsey with a new assignment. She is to travel under an assumed identity to the port city of Sunderland and there await further instructions. Ellie, ever-ready to aid her country, heads north, her safe-cracking tools in tow. But before she can rendezvous with the major, she witnesses an unnatural death. A man falls dead in the street in front of her, with a mysterious missive clutched in his hand. Ellie's instincts tell her that the man's death is connected in some way to her mission. After she is reunited with Major Ramsey, the pair discovers that the dead man had ties to a counterfeiting operation, supplying German spies with fraudulent British currency to use in their operations. Even more troubling, it quickly becomes apparent someone high-up in the operation is helping to smuggle those spies into England across the North Sea. Soon, Ellie and the major are locked in a battle of wits and a race against time with an unknown and deadly adversary. With German bombs dropping on the city and a would-be assassin shadowing their every move, it will take all of Ellie's resourcefulness and Major Ramsey's fortitude to unmask the spymaster and avert disastrous consequences—for England and for their own lives.