June 1945. Hitler has triumphed, Britain is under German occupation and America cowers under the threat of nuclear attack.

In the dead of night, a figure flits through the ruins of Dryburgh Abbey, searching for a hidden document he knows could change the course of history. The journal he discovers, by a young soldier, David Erskine, records an extraordinary story.

When the Allies drive the Germans out of France and victory seems imminent, Erskine is in Antwerp, where he witnesses a world-changing reversal of fortune. From a high vantage point, he watches a huge mushroom cloud rise over London: an atomic bomb has been detonated by the Germans in a last desperate roll of the dice.

Captor becomes captive and Erskine is held as a POW in his own land. As the brutal grip of the occupying forces tightens, he is determined to join the resistance. A daring escape leads him and his fiance Katie on a breathless chase to the university town of St Andrews, where the Germans have established a secret research laboratory. When it becomes clear what its purpose is, David, Katie and their small, trusted band must adopt a desperate and audacious plan to thwart Nazi domination...