Just before dying from wounds received in a skirmish with Indians Capt. Forsythe orders his cavalry troop's doctor, Capt. Robert MacClaw, to take command. His men don't like it and think that Sgt. Elliott should have been put in temporary command until they reach the Fort. MacClaw admits he knows little of battle tactics but takes charge only with the promise that he will do the best he can. If anything, the men are embarrassed at having such an inexperienced man leading them and MacClaw agrees not to let on that he's a doctor. When they arrive at a staging post they are ordered by the Colonel in command of a group of infantry to escort a wagon train of settlers moving west. There may be smallpox among them however and MacClaw is caught between his promise to his men and the demands of Martha Cutting who is trying to deal with the epidemic.