1940: Weeks after the evacuation of Dunkirk, Germany is poised to invade a near-defenseless Britain. To safeguard the Crown Jewels from the Nazis, Winston Churchill devises a daring gamble to have them shipped overseas. The priceless artifacts will be secretly removed from the Tower of London and driven north to Scotland by two operatives posing as a young married couple, to be taken from there to Canada.

Caitrin Colline—a Welsh coalminer's daughter and an ardent socialist—will play the wife of Lord Marlton, Hector Neville-Percy. A less likely couple is at first difficult to imagine. Yet Caitrin's bold, streetwise confidence and sharp wits complement Hector's social ease and connections, essential to a second part of their mission: uncovering Nazi sympathizers within the highest ranks of Britain's aristocracy.

Battling enemies within and without, Caitrin wonders if anyone in their circle can be trusted—even her partner. And when unexpected events catapult her into a life-or-death chase across the continent, the morale of a nation and the fate of Europe itself in the balance.