Newspaper reporter Tim Rourke keeps writing articles that attack the police department for its failure to solve a chain of murders, which nearly leads to the reporter's death. He calls in private detective Michael Shayne, who turns up a blonde and a blackmailer.

Murder mystery programmer from Republic pictures

A London curator loses the Mona Lisa to a collector, who discovers it's a fake.

A private detective is offered a job protecting a rich business man from suspected blackmail. Before he can accept the case a murder is uncovered.

Spotted after he microfilms secret U.S. Navy documents, foreign agent Rattick is killed when he tries to make a getaway. Naval Intelligence officer Captain Wright and Operative Dale are assigned to investigate and determine who is behind the spy syndicate for which Rattick worked. They bring in the services of Agent Tom Norman, who bears a strong resemblance to Rattick.

Michael Lanyard is suspected of stealing two fabulous diamonds from a vault in Scotland Yard, where they were being held for safekeeping, but the Yard can't prove he did it. Later, Lanyard is summoned by a member of the nobility to help the latter raise money to pay a blackmailer. Lanyard later finds evidence to reveal the diamonds as having been stolen by a famous stage star.