Neale and Pedro fly cargo between Chungking and Calcutta. When their buddy Bill is murdered they investigate. Neale meets Bill's fiancTe Virginia and becomes suspicious of a deeper plot while also falling for her charms.

Three American pilots, Bill Cunningham, Neale Gordon and Pedro Blake, fly a route from Chungking, China to Calcutta, India, where they share an apartment at the Hotel Imperial. On one trip, when Neale and Pedro's plane is forced to land in the mountains, Bill rescues them and then rushes back to Calcutta, where he and his fiancée, American Virginia Moore, are having an engagement party. When Neale and Pedro arrive in Calcutta, however, they learn that Bill has been strangled to death. Marina Tanev, a nightclub singer who is in love with Neale, informs them that Eric Lasser, who runs the nightclub, canceled the engagement party. Virginia tells Neale that the night Bill was killed, he left her in the hotel bar and never returned. Neale forces Virginia to confess she was not in love with Bill, then tears an expensive diamond necklace from around her neck. During a flight to Chungking, Pedro meets Mul Raj Malik, an Indian merchant, and Malik tells him to visit him at his import-export shop in Chungking. Back in Calcutta, a jewelry merchant named Mrs. Smith confirms that Bill bought Virginia's necklace himself, and Neale learns that Bill deposited a $7,000 check from Lasser's gambling establishment before he died. Later, Neale apologizes to Virginia for suspecting her, and over a drink, they begin to fall in love. At night, Neale boards one of his and Pedro's planes, and after discovering a bag of jewels hidden in the floorboards, he is nearly killed with a posse noose, the same device used on Bill. Neale gives the jewels to Pedro to place in a safe deposit box, and with only a brooch and the bag in his possession, returns to the hotel, hoping to bait the smugglers out of hiding. Malik pulls a gun on Neale, but then leaves and is shot in the hall. When Neale shows the brooch to Marina, she warns that Bill found out about the shipment in the hotel and was called away from Virginia by an unknown informant. Again suspicious of Virginia, Neale visits her room, but it has been ransacked and she is missing. Neale later shows the brooch to Mrs. Smith, who explains that Malik used to be her partner in running smuggled goods and that after he found out that someone was successfully running goods to Chungking, he tried to get in on the deal. British police officers led by Captain Hendricks arrest Neale, whose gun they have, for Malik's murder. Pedro, however, claims the gun is his so that Neale can be released to find the killer. Virginia, in hiding, sends word to Neale, and when he visits, she confesses her love for him and they kiss. The next morning, Neale learns from the hotel desk clerk that Bill and Virginia were not at the hotel bar the night he was murdered, as Virginia had claimed. Furious at Virginia's duplicity, Neale brings the jewels to her to test her greed and slaps her into confessing that, as part of Lasser's smuggling ring, she was to seduce the pilots who were running the goods. She says she never meant to harm Bill, who discovered Lasser placing a shipment in his plane, and contends that she held a gun on Bill to keep him from talking, but that Lasser strangled him. Through false tears, Virginia pulls a gun from a drawer as Lasser enters. Neale disarms Virginia and kills Lasser during a struggle, then calls Hendricks. As she is arrested, Virginia swears her love to Neale. Later, when Marina sends Neale off on his next flight, and advises him that he is safer tangling with mountains than with women, they kiss.