On the French coast, unlucky Marie Galante is abducted and forced to board an American cargo ship bound for the Panama Canal. When an escape attempt leaves Marie high and dry in the Yucatan, she takes work as a nightclub singer to earn her safe passage to the Canal region. But Marie faces bigger problems when she gets mixed up in a destructive plot against the U.S. Naval fleet, and so she accepts the kindly assistance of secret agent Dr. Crawbett.

After notorious jewel thief Flambeau meets Evelyn Fischer during a raid on a casino, he falls deeply in love with her. Later Flambeau sends notes to both Leopold Fischer, who unknown to him is Evelyn's uncle, and Father Brown, in which he vows he will steal from them the ten diamonds that comprise the "Flying Star." Flambeau intends to give these diamonds to Evelyn. Father Brown, whose gold cross contains some of the Flying Star diamonds, is determined to meet Flambeau before he is arrested, to reform and redeem his soul.

At a reception given by Arthur Hilton at his Sussex home the conversation turns to the subject of danger, with Hilton recalling a case in which he was involved as a Natal police commissioner. In it there were three guilty persons, but only one of them was hanged; the other two were sentenced to long terms, vowing vengeance on Hilton. Unknown to him, the same two men are now among his guests, and are determined to have their revenge.

A secretary takes the blame when his fiancée's father ruins his oil company.

Fresh from Chinatown in New York, Harry Young has taken over the illegal import business in the seamy Limehouse district of London, where he cold-bloodedly disposes of rivals and runs a smoky nightclub. He falls for a low-class, white pickpocket, diminishing his pride in the Chinese half of his heritage and sparking the jealousy of the nightclub's moody star performer.