Date with Darkness

Donald Hamilton's debut novel.
The hero is Lieutenant Philip Branch, USNR, who has been serving in the Navy during WWII at a desk job in Chicago, Illinois. He is soon to be released from active duty and is spending a couple weeks leave in New York City. There he meets Jeanette Duval, wife of a French collaborator, who is trying to smuggle her husband into the U.S. Trying to thwart her efforts, a group of idealistic French patriots want to capture Mr. Duval and see to it that he is punished for his collaboration with the Nazis. They all want Lieutenant Branch to assist them, and he spends most of the book trying to figure out who the good guys and the bad guys are.