Originally Aired: May 25, 1958

Gunsmoke #320, "Blue Horse," finds Marshal Matt Dillon transporting a murderer named Hobb Cannon back to Dodge City across the dry plains. When Matt's horse steps in a hole and falls, the Marshal suffers a badly broken leg. With no choice but to send Chester riding two days back to Dodge for help, Matt finds himself stranded and vulnerable, left alone with the dangerous prisoner. As fever sets in and his condition worsens, the cunning Cannon sees his opportunity and begins to wait for the right moment to make his escape.

The situation grows more desperate as Matt struggles to maintain control despite his injury. When Cannon finally makes his move to kill the helpless Marshal and steal his horse, an unexpected figure emerges from the darkness. Blue Horse, the escaped Indian sub-chief that Lieutenant Eldridge's cavalry troops were searching for earlier, suddenly appears at the crucial moment. The encounter sets up a tense standoff that will determine whether Matt survives long enough for Chester and Doc Adams to arrive with help.