The
Union army in the
American Civil War is in desperate need of new horses. A
Confederate spy in Colorado has been informing freeboot
horse rustlers of the timing and route of herds being driven by the Union army, enabling the horses to be seized and resold to the South. Charged with cowardice when he abandons his herd, Major Lex Kearney is expelled from the Union army with a
dishonorable discharge and a yellow streak painted down his back. His wife Erin informs him that their son has run away in shame. Kearney is baited by his archenemy Captain Tennick into trespassing on Army premises, invoking the death penalty. In the brig with captured raiders Austin McCool and Pete Elm, Kearney aids their escape and accompanies them to the main hideout. An ambush is prepared with the goal of killing McCool to remove the actual head of the operation. As arranged, Tennick kills McCool but dies in the process, stranding Kearney without a contact man. He continues his ruse, entering into a business partnership with Elm. A shipment of the new rapid breach-loading
Springfield Model 1865 rifles is due, offering a five-to-one potential firepower advantage for the Union troops. The rustlers are notified of the pending arrival. Kearney has accepted a fake discharge so that he can execute a top-secret undercover assignment as a Union counterintelligence agent to find the rustlers and the spy who has been giving them the information. The chief traitor is Colonel Hudson, the Union fort commandant, who has always been sympathetic to Kearney and his wife. Discovering Kearney's role, Hudson orders the murder of everyone who knows the truth of his role and frames Kearney for treason. Sympathizers at the fort help Kearney escape, and together they hijack the Springfield rifle shipment for the showdown with the horse thieves. Elm is killed and Kearney attempts to capture Hudson alive to face military justice. ==Cast==