The film was released on September 22, 1939, the day after President Franklin D. Roosevelt signed the Neutrality Act allowing "Cash and Carry" provisions for countries fighting Germany and a little over four months after another Warner Bros. anti-Nazi film Confessions of a Nazi Spy .
The film opens with a description of the Black Tom explosion of a munitions supply located in Jersey City on the Hudson River. The explosion, which occurred during World War I was an act of sabotage by German agents.
Staring Joel McCrea as Barry Corvall, the son of a recently deceased American diplomat, who has just gotten married. When he discovers that his new wife (Brenda Marshall) is a possible enemy agent, he resigns from the diplomatic service to go undercover to expose an espionage ring planning to destroy American industrial capability before World War II. Traveling on a train in Germany, Corvall attempts to swipe a briefcase with documents in an attempt to prove that the Nazis, have been infiltrating vital industrial centers in the United States. With the help of his wife, he tries to foil the plans of the Nazi spy (Martin Kosleck).