It is spring, 1940, and the yet to be named Manhattan Project is already stalled. Franklin Roosevelt has been told that the detonation of an atomic bomb is dependent upon a specially designed charge of conventional explosive and that only one man, a Polish mathematician and physicist, has worked out the mathematical formulas for its design. Unfortunately, the scientist is a prisoner in a Soviet concentration camp in Siberia. Roosevelt enlists a close friend and confidant, William Donovan, to rescue the Pole from the Gulag. Donovan calls upon a Canadian bush pilot, William Tavish, to head the mission. Tavish, who is currently flying for the RAF in the beginning Battle of Britain, wants no part of Donovan's plan but is forced to volunteer. It is a daring mission onto foreign soil with the fate of the atomic bomb and possibly victory in the coming world war hanging in the balance.