At the breaking of the Civil War the garrison of Fort Laramie splits between the sympathezers of the two different factions, but when the fort is attacked by the Sioux, they unite their forces to fight them.

Ex-Confederate Bedloe Mason and his four sons ride into a small Western town with robbery in mind. Hearing a suspicious "click," Wes Mason whirls and shoots dead a boy playing with a cap pistol. The Mason clan then flees but Gray Mason, feeling remorse, decides to return to the town. He winds up at the home of John and Nora Willoughby who, unknown to him, are parents of the dead boy. Nora recognizes him as one of the Confederates but keeps quiet, wishing to avoid more violence. However, when John learns of Gray's true identity, he determines to avenge his son's death