In post-World War II Asia, three American pilots—Neale Gordon, Alan Ladd, Bill Cunningham, John Whitney, and Pedro Blake, William Bendix—fly a route from Chungking, China to Calcutta, India. They live at the Hotel Imperial in Calcutta. When Neale and Pedro's aircraft is forced down in a mountainous area, Bill comes to the rescue.
Bill's fiancée, Virginia Moore, Gail Russell, at an engagement party tells Neale and Pedro that Bill has been strangled. Nightclub singer Marina Tanev, June Duprez, says Eric Lasser, the nightclub owner, canceled the engagement party on the night Bill was killed. Tearing an expensive diamond necklace from her neck, Neale confronts Virginia, making her confess she was not in love with Bill.
During a flight to Chungking, Pedro meets Indian merchant Mul Raj Malik, Paul Singh, who tells him to visit him at his import-export shop. In Calcutta, Mrs. Smith, Edith King, a jewellery merchant reveals Bill bought Virginia's necklace and deposited a $7,000 check before he died. Neale is still wary of Virginia's involvement in his friend's death, and when he discovers a bag of jewels in the floorboards of one of their aircraft, he has to fight for his life.
Giving the jewels to Pedro, Neale returns to the hotel, hoping to catch the smugglers, but Malik confronts him and is shot as he leaves the room. When Neale shows a jewelled brooch to Marina, she warns that Virginia knows more about the night Bill died. Going to her room, Neale finds it has been ransacked and Virginia is missing.
British police officers led by Inspector Kendricks, Gavin Muir, arrive to arrest Neale for Malik's murder. Pedro claims the gun that was used in Malik's murder was his. Neale is released and he pledges that he will find the real killer. Virginia contacts Neale and tells him she loves him, but he is still suspicious of her motives. When the hotel desk clerk who was there the night Bill was murdered contradicts Virginia's story, Neale wrings the truth out of her. She was part of the smuggling ring, with her role to get close to the pilots who were flying in and out of Calcutta, until Bill got wise to the scheme. She held a gun to Bill's temple, but it was Lasser who strangled him.
Lasser bursts in, and Virginia tries to shoot him but is disarmed by Neale, who kills Lasser during their struggle for the gun. Neale then calls in Kendricks, who arrests Virginia, still professing her love for Neale. Later, when Marina goes to the airport, she tells Neale that tangling with mountains is safer than his dealing with women. The two embrace and kiss as Neale sets off on his next flight.
