On their way to Denver, Beau and Bart Maverick pick up $6,500 in a poker game at Stop Gap. They decide to wire the money to Denver through the Hulett Telegraph Company. They discover the company is a fake and that the telegraph line leads to a cave two miles away where the crooks stash the customers' money and send phony messages in return. The cousins devise a scheme to recover the money and put the company out of business.

A money-making machine costs Bart a bundle. His cousin (Kathy Bennett) has just bought one with the $10,000 he lent her.

While trying to get a young girl's romance back on the right track, Bart gets involved in a train robbery to end all train robberies.