The editor of the New York Globe (Harry Davenport) is concerned about the situation in Europe and the growing power of Adolf Hitler and Nazi Germany. After searching for a good, tough crime reporter, he appoints Johnny Jones (Joel McCrea) as a foreign correspondent, under the pen name "Huntley Haverstock".
The reporter's first assignment is Stephen Fisher (Herbert Marshall), leader of the Universal Peace Party, at a party held by Fisher in honor of a diplomat named Van Meer (Albert Bassermann). On the way to the party, Haverstock sees Van Meer entering the car which is to take him to the party, and runs to interview him; Van Meer invites him to ride along. At the party, Haverstock meets Fisher's daughter, Carol (Laraine Day). Van Meer disappears mysteriously. Later, Fisher informs the guests that Van Meer, who was supposed to be the guest of honor, will not be attending the party; instead he will be at a political conference in Amsterdam.
At the conference, Van Meer is shot in front of a large crowd by a man disguised as a photographer. Haverstock commandeers a car to follow the assassin's getaway car. The car he jumps into happens to have in it Carol and Scott ffolliott (George Sanders), another reporter who explains that the capital letter in his surname was dropped in memory of an executed ancestor. The group follows the assassin to a windmill in the countryside.
While Carol and ffolliott go for help, Haverstock searches the windmill and finds a live Van Meer the man who was killed was an impostor. The old man is drugged and unable to tell him anything. Haverstock is forced to flee when the kidnappers become aware of him. By the time the police arrive, the villains have escaped with Van Meer in an airplane.
Later, back at Haverstock's hotel room, two spies dressed as policemen arrive to kidnap him. When he suspects who they really are, he escapes out the window and into Carol Fisher's room.
Haverstock and Carol board a British boat to England, and while a furious storm thunders overhead, he proposes to her. In England, the two go to Carol's father's house, where Haverstock sees a man whom he recognizes as one of the men at the windmill. He informs Fisher, but Fisher ignores him, saying that he will send a bodyguard to protect him. However, the bodyguard (Edmund Gwenn) repeatedly tries to kill Haverstock instead. When the assassin tries to push him off the top of the Westminster Cathedral tower, Haverstock steps aside just in time and the "bodyguard" plunges to his death instead.
Haverstock and ffolliott are convinced that Fisher is a traitor, so the two come up with a plan, with Haverstock taking Carol to the countryside, while ffolliott pretends she has been kidnapped to force Fisher to divulge Van Meer's location. However, Haverstock and Carol argue, and she returns to London. Just as Fisher is about to fall for ffolliott's bluff, he hears her car pull up.
ffolliott follows Fisher to a hotel where Van Meer is being held. Just as Van Meer is being forced to divulge the information the organization wants, ffolliott distracts the interrogators. When Haverstock arrives, Fisher and his bodyguards escape, leaving Van Meer behind. Van Meer is rushed to the hospital in a coma.
In the meantime, England and France have declared war on Germany. Then, while the group are on a Short Empire "Clipper" plane to America, Fisher confesses his deeds to his daughter. Despite this, Carol blames Haverstock for not really loving her and only wanting to pursue her father. He protests that he was just doing his job as a reporter, but Carol refuses to listen. Seconds later, the plane is shelled by a German destroyer and crashes into the ocean. The survivors perch on the floating wing of the downed plane. Realizing that it cannot support everyone, including his daughter, Fisher commits suicide by allowing himself to drown. Jones and ffolliott attempt to save him, but are unsuccessful. Shortly after, they are picked up by an American ship.