Detective Guy Johnson's client, Willie Heywood, is framed for murder. While Guy hides him so he can catch the real killer, both of them are nabbed by the police, tried, convicted and sentenced to jail: Guy for a year with Willie to be executed. On the way to jail, Guy comes across a clue and escapes from the police.
In coastal Cornwall, England, during the early 19th Century, a young woman who's come there to visit her aunt, discovers that she's married an innkeeper who's a member of a gang of criminals who arrange shipwrecking and murder for profit.
When a confused eyewitness identifies New York City cabbie Brick Tennant as a killer, he is sentenced to death for a murder that he wasn't involved in. Though no one is willing to listen to the innocent prisoner's pleas for freedom, Brick's faithful fiancée, Mary, knows that her lover is innocent because she was with him when the crime was committed. As the scheduled execution draws ever nearer, Mary begins to investigate the murder herself.
Johnnie learns crime from petty thug Frank Wilson. When Wilson kills a pawnbroker with a gun stolen from Johnnie's sister Madge's fiance Fred Burke, Fred goes to Sing Sing's death house. Wilson uses all the pressure can to keep Johnnie silent, even after he and Johnnie themselves wind up in the big house.
Suave private detective Simon "The Saint" Templar arrives in San Francisco and meets Val, a woman whose police inspector father killed himself after being accused of corruption and dismissed from the force. Convinced of the man's innocence, Templar takes it upon himself to vindicate the memory of Val's father. To do so he must take on the city's most dangerous criminal gang, while also battling hostile members of the police department.
Physician Carole Nelson, suspected of having ties to notorious gangster Joe Gurney, must prove her innocence or the Medical Board will revoke her license. When Gurney seeks her out for treatment after being shot, it could be the break Nelson needs. Now she has a chance to use her medical know-how to outwit Gurney and his goons and reestablish her professional reputation.
A chemical manufacturer is killed just after asking detective James Wong to help him. So detective Wong decides to investigate this as well as two subsequent murders.
Jim 'Socker' Conway, former boxer and FBI hero, is maneuvered for political reasons into a do-nothing job in the district attorney's office. Meanwhile, he meets wild debutante Letty Lane, girlfriend of mob mouthpiece Steve Lawrence; and Letty's much nicer sister Susan. Now the slot machine gang brutally beats Jim's friends Franz and Otto. And Jim finds a way to use his nominal position to go into the racket- busting business. But his success puts Letty in deadly peril...
A wealthy society doctor decides to research the medical aspects of criminal behaviour by becoming one himself. He joins a gang of thieves and proceeds to wrest leadership of the gang away from it's extremely resentful leader.
A young girl is travelling to London to find work. Arriving at the station, she meets a man who has been stabbed by a member of a gang of crooks involved with greyhound racing. She becomes a suspect, but flees the scene in order to deliver a message to the dead man's brother. She is protected from the police by a night club entertainer, who she learns is the man she is seeking.
Mobster "Baby Face" Martin returns home to visit the New York neighborhood where he grew up, dropping in on his mother, who rejects him because of his gangster lifestyle, and his old girlfriend, Francey, now a syphilitic prostitute. Martin also crosses paths with Dave, a childhood friend struggling to make it as an architect, and the Dead End Kids, a gang of young boys roaming the streets of the city's East Side slums.
When a hard-working machinist loses a promotion to a Polish-born worker, he is seduced into joining the secretive Black Legion, which intimidates foreigners through violence.
Pépé le Moko, one of France's most wanted criminals, hides out in the Casbah section of Algiers. He knows police will be waiting for him if he tries to leave the city. When Pépé meets Gaby, a gorgeous woman from Paris who is lost in the Casbah, he falls for her.
Karl Anton Verloc and his wife own a small cinema in a quiet London suburb where they live seemingly happily. But Mrs. Verloc does not know that her husband has a secret that will affect their relationship and threaten her teenage brother's life.
Nick and Nora Charles investigate when Nora's cousin reports her disreputable husband is missing, and find themselves in a mystery involving the shady owners of a popular nightclub, a singer and her dark brother, the cousin's forsaken true love, and Nora's bombastic and controlling aunt.