Racial tensions flair when a black officer joins a Cavalry troop fighting the Indians.

Scout Jess Remsberg rescues Ellen Grange, who had been a captive of the Apaches for more than a year, and takes her back to her husband at Fort Creel. When her husband denounces her for not killing herself when captured by the Apaches, Mrs. Grange rides off during the night. The next morning Lieut. Scotty McAllister and a troop of raw recruits set out for Fort Concho with Jess as scout. Jess is seeking to avenge his Comanche wife's murder by finding the unknown white man who profited from her death by selling her scalp. Also in the party are Grange, who is taking a wagonload of goods to Concho, and Toller, a Negro ex-cavalryman who now makes his living breaking in horses for the cavalry. Moving out ahead of the troop into Indian country, Jess finds Mrs. Grange in an Apache camp. As he once more carries her away, he sees that she has a child bundled in her arms. She explains that he is her half-breed son, born out of a union between herself and the Apache chief's son. Returning with Mrs. Grange to Scotty's troop, Remsberg finds they have been ambushed by Apaches; casualties are heavy and the water supply has been destroyed. After outwitting and routing the Indians at Diablo Canyon, where there is fresh water, Remsberg rides off for reinforcements. At Fort Concho he learns that the unknown white man he is seeking is Will Grange. Riding back to Diablo, Jess joins in the savage fighting, during which Scotty is killed and Grange is captured. When reinforcements arrive and the Apaches surrender, Jeff, Toller, Mrs. Grange, and four soldiers are all that remain of the original party. Jeff goes in search of Grange and finds him strapped to a wagon wheel hung over hot coals. He is barely alive and begs Jess to shoot him. Instead, Jess hands him a pistol, and as he walks away, a shot rings loudly.