Christmas Day 1943, Arisaig, Scotland. The body of beautiful, well-connected Polish SOE agent Krystina Kowolska is found in the gardens of the country house where she's been preparing for a vital mission to France. The question is, was she already dead when she was hanged?
Two days later, resistance double agent, Investigator Jan Kalisz of the Warsaw Kripo is flown to Britain where Winston Churchill himself tasks him with finding Krystina's killer, before the cracks in Britain's alliance with Poland become fractures.

Yet Arisaig is a place of secrets where everyone is a trained killer, and Kalisz discovers that Krystina had her demons – and her enemies. Was she the hero her record suggests or the traitor the whispers hint at?