A gunhand named Lane is hired by a widow, Mrs. Lowe, to find gold stolen by her deceased husband so that she may return it and clear the family name.

A Pinkerton agent masquerades as a criminal in order to infiltrate a gang of counterfeiters that is using wealthy widow Lucy Randall as a front. Arriving at the gang's hideout the Dawson ranch, Red discovers that the counterfeiting ring is headed by Mrs. Randall's attorney J. Richard Spencer and Dawson himself.

Detective Allan Pinkerton, working for the Union, becomes obsessed with Southern socialite Rose O'Neal Greenhow, a spy for the Confederacy.

Charles Starrett makes his final appearance as The Durango Kid, this time as Steve Reynolds, a postal inspector who has gone underground to catch the bad guys. His longtime sidekick, Smiley Burnette appears as an itinerant optometrist who is hardly in the plot line of the film. Jock Mahoney plays Jack Mahoney, an eastern educated dude who has come back home. The Durango Kid teaches Jack how to draw and fire a six-gun, and the two ultimately work together to bring the outlaws to justice.

Two newly-appointed postal inspectors, Frank Marshall and 'Slim" Hewitt, set out to track down the sender of a time-bomb to a U. S. Senator and, during their investigation, run across a hooded organization that is terrorizing an American city. They also meet Don Foster, who is loud in his condemnation of the terrorists, and his sister, Nancy, who fears for her brother's life.

Postal inspectors investigate a con man who uses the identities of others to falsify credit card purchases. Stealing credit card offers from mail boxes, he obtains cards in others' names, makes many purchases until the card is maxed out, but is always careful to pay minimum balances. According to the story, it is possible for individuals such as this to run many credit cards at a time without being caught.

Al Goddard, a detective who works for the United States Postal Inspection Service, is assigned to arrest two criminals who've allegedly murdered a U.S. postal detective.

Investigators set out to capture a gang of thieves transporting stolen cash through the U.S. mail.

Stolen way back in 1880, a sack of United States mail is discovered in an old attic in 1942. The letters are finally delivered, profoundly affecting the lives of the recipients.

Postal inspectors track down money stolen from a railroad car.

Two bounty hunters both pursue the brutal and sadistic bandit, El Indio, who has a large bounty on his head.

The fiery, impulsive, yet pure-hearted Lasca lives in a Mexican settlement near the Rio Grande with her twin brother Ricardo and their aunt. She falls in love with cattle rancher Anthony Moreland, whose teasings bring out her jealous temper, but Moreland, although fond of Lasca, thinks of her as a child. Seeing the flirtatious, though engaged, Clara Vane fall in love with Anthony, Lasca, in a vicious fit, stabs his wound and begs forgiveness.