Two cowboys try to protect railroad workers from rampaging Indians.

In the era when railroads are first being forged across the United States, Southwestern Railroad is plagued by raids, during which their supplies are stolen. Bill Borman, who is in charge of Southwestern's construction, brings in Marshal Cliff Tyler for protection, and although Tyler drums up support, he needs horses for his patrolmen. In nearby Cold Springs, Borman's assistant, Hanley, arranges to buy horses from Betty Wallace's ranch, but when she tells her foreman, Tip, about the sale, he informs Mel Carson, a saloon owner who is being paid by the owner of a stagecoach line and a judge who dislikes law and order to prevent the construction of the railroad. Carson orders Tip to rustle the horses and rob the buyers, and after Tip murders several men during the robbery, he hides the herd of horses in a canyon. As they are already working for Borman, Tyler sends former lawmen Hoot Gibson and Ken Maynard to Cold Springs to work undercover and help rout the saboteurs. Hoot and Ken first make contact with Tyler's son Bob, an inexperienced marshal whose "by the book" methods have been ineffective. After Bob deputizes them, Hoot and Ken question Betty, but she has no clues as to the identities of the saboteurs. Ken escapes a near ambush by Carson's men, but later joins Carson in a card game. Ken wins the game and matches the serial numbers on Carson's bills to those stolen from Hanley. Bob wants to arrest Carson immediately, but Hoot and Ken are determined to retrieve Betty's horses. Hoot and Ken try to trick Carson into leading them to the hidden herd, but Carson is suspicious and arranges for an Indian tribe to attack the next railroad shipment. One night, Hoot and Ken trick Tip and his gang into thinking that they are surrounded. After overhearing the men reveal the location of the horses, Hoot and Ken slip away and take the herd, and Tip does not realize they are free until morning. Betty gathers a group of trustworthy ranch hands to herd the horses into town, while Hoot gathers proof of the conspiracy. When the horses stampede through the town, a gunfight erupts between Hoot and Ken and the gang. Hoot and Ken are victorious, and after arresting the gang, they take the stolen money from Carson's safe and buy the horses from Betty's ranch.