On the train from Baghdad to Istanbul, an American comes into possession of a package sought by both Nazi and Russian agents--something for which a beautiful woman has just been murdered--in Background to Danger. World War II: Turkey remains neutral, wedged between Russia and the Nazi-controlled Balkans. While the fate of one nation, and possibly the outcome of the war, hang in the balance, American Joe Barton (George Raft) agrees to hold an envelope for beautiful Ana Remzi (Osa Massen) until their train arrives in Ankara. But when Joe tries to return the envelope, he finds Ana dead. Now, with the Russian Zaleshoff (Peter Lorre), his beautiful sister Tamara (Brenda Marshall), and Nazi agent Colonel Robinson (Sydney Greenstreet) pursuing him, Joe realizes he is holding the secret Nazi blueprint for the invasion of Turkey.