A government pilot (George Brent) falls for a woman (Isa Miranda) helping her partner (John Loder) smuggle diamonds out of South Africa.

In 1869, the United States begins a railroad mail service to the West Coast which proves highly tempting to train robbers, in particular an organized gang with one of the mail's supposed guardians in their pay. Prizefighter Steve Davis, a former army intelligence man, is hired to track down the gang and save the Territorial Mail Service. Steve goes undercover in territorial prison, leans Morse Code from a fellow prisoner, breaks jail, infiltrates the gang...and finds time to romance dance-hall singer Mary, who proves to have hidden depths...

A manipulative diva blackmails a married man and insults her secret lover, leading to her murder. As the husband tries to cover his tracks, the lover sabotages him and suggests turning the case into a TV show episode.

After hearing that a famous actress is dying in a hospital after being hit by a car, a reporter goes to the hospital to interview the actress. She then tells the reporter that her wealthy fiance, who was killed in an accident several years before, was actually murdered. Before long the reporter finds herself in a web of corruption, mental illness and murder.

Roger Quain, escorting two zoo-bound black panthers on the train from Milan to Paris, is unaware that a Western agent, Catherine Ullven, has hidden a microfilm in the collar of one of the animals. But when the train is derailed in the Swiss Alps and the panthers escape, she is forced to involve him in her mission, which now includes enemy agents hunting the microfilm, the animals, Catherine and Roger.

A innocent dentist is murdered and the only apparent motive seems to be to steal a set of dental x-rays. To the police it looks like an accident, but private eye Brad Runyan thinks there's more to it.

A young lawyer is determined to identify who is murdering members of a wealthy New York publishing family.

After the King of Rovenia has been assassinated, Holmes and Watson are engaged to escort his son to Europe via Algiers, aboard a transatlantic ocean liner which also carries a number of suspicious persons, any of whom may be involved in a plot to also assassinate him.