There is a problem with foreign nationals using Cuba as a convenient jumping off point for illegal entry into the United States. So U.S. Immigration Service Agent Peter Karczag (John Hodiak) is sent to Havana posing as a Hungarian frustrated with the legal immigration process and open to an alternative. By this means he uncovers the human smuggling ring run by Palinov (George Macready). He also meets concentration-camp refugee Marianne Lorress (Hedy Lamarr), a Viennese working in a nightclub and one who has paid to be smuggled into the United States. When Karczag falls in love with her, he becomes conflicted, not wanting her to be among those he plans to have captured in his operation. So he tries to persuade her to stay in Cuba instead of being secretly flown to the United States. Will he succeed? What if his cover is blown?