The Stark Gang has brazenly robbed the bank in Dodge City, but a diversion Jim Stark had planned did not work as expected, primarily because Clell Williams was impatient and veered off the plan. The result was that Matt Dillon and Festus Haggen returned to Dodge earlier than expected. As a matter of fact, they come riding into town just as the Stark Gang is making their exit. One of the gang, Jeff Fraley, is shot and seriously injured during the ensuring gunfight.
Les McConnell was supposed to stay behind in Dodge for another day, but that depended on the robbery plan working as expected. When Jeff Fraley was shot, his brother Pence went after Doc Adams, wisely realizing Jeff would need a doctor's care. McConnell set several fires to keep the Dodge City citizens occupied and left with Pence Fraley and Doc.
When the gang arrives back at the Early farm they were using as a meeting place/hideout, Jim Stark confronts Williams about his failure to execute the plan properly. Jim Stark also gives Mr. and Mrs. Early (and the viewer) a little speech justifying his actions. Stark tries to make the case that he is some kind of Robin Hood figure stealing from banks, trains, and "rich Northerners" and giving the plunder to more deserving people. No one really buys Stark's reasoning, not even Stark himself.
The story now shifts to a more familiar cat-and-mouse scenario where Marshal Dillon, Festus, and the posse from Dodge City is pursuing the gang, but there are surprising developments along the way as the story builds to an inevitable conclusion, particularly as both the "cats" and the "mice" suffer from attrition along the way, and Jim Stark descends into an increasing state of madness at his inability to control the situation.
Arguably, this is the best two-part episode in the entire Gunsmoke series. The cast, the acting, the story, and the direction are all top notch. The episodes could easily be edited into a movie. The two episodes offer some intense, compelling viewing.