Under Fire (1926)

Lt. Tom Brennan is cashiered from the 7th Cavalry on two charges, both unjust: that of deserting his men in the face of a cruel Indian attack, and of entertaining a married woman in his quarters after hours. Tom wanders into the desert and is picked up half-dead by Yuba Bill, a prospector with whom he goes into partnership. The Indians go on the warpath, and Tom rides to the fort and warns the colonel. Tom's innocence is established by the confession of an enlisted man, and Tom is reinstated to the service with full honors, renewing his engagement with Margaret Cranston.