Nathan Silverman grew up in Berlin in the 1920s, the son of a homemaker and a theoretical physicist. His idyllic childhood was marred by increasing levels of antisemitism, and after his uncle is arrested on Kristallnacht, he leaves Germany for New York City with only his mother's wedding ring to sell for survival.

While attending Columbia in 1941, Nathan decides to enlist in the military. To his surprise, he is selected for a special assignment; he is trained as a spy, and ordered to report to the Manhattan Project. There he learns that the Allies are racing to develop a nuclear weapon before the Nazis, and a German theoretical physicist is hoping to defect. The physicist was a friend of his father's, and Nathan's mission is to return to Berlin and smuggle him out of Europe.

Nathan will be accompanied by Dr. Allison Fisher, a brilliant young scientist; he travels to her lab at the University of Chicago for a crash course in nuclear physics, then they embark on their adventure. Nathan and Allison soon develop feelings for one another, but as their relationship deepens they move ever closer to their dangerous goal. Will they be able to escape Europe with the defector and start a new life together, or will they become two more casualties of war?

An Affair of Spies is an action-packed tale of heroism and love in the face of unspeakable evil, author Ronald H. Balson's most thrilling novel yet.