March, 1938 Otto Lehman arrives in New York on the S.S. Osthafen to be immediately confronted by two men with FBI badges . . . only, that isn't his real name and the men aren't with the FBI. The next day Lehman is found tied to a chair, beaten to death and naked, in an abandoned Brooklyn warehouse.

The sole witness to the crime, Andrew Blake, a homeless man struggling through the Great Depression, claims those responsible were speaking German. With the threat of the perpetrators being Nazis, President Roosevelt's own covert counter-intelligence agent Jacob Welker is brought in to investigate.

Welker recruits Blake along with Lord Geoffrey Saboy, a British 'cultural attache', and his wife Lady Patricia, to help him to thwart a Nazi terrorist attack. But who exactly are the Nazis, what is their target and when will they strike?