Jonas, the owner of the Dodge City general store, leaves his clerk in charge of the day's money one rainy night. As the clerk is totaling up receipts and cash, a masked gunman enters the store. The robber's mask drops and he shoots the clerk to prevent him from being identified. Matt Dillon asks the clerk who did it, but he only has time to say the last name - Cumbers - before he dies.
The problem is there are two men named Cumbers -Frank and Nate, as well as their rather overbearing mother. Dillon goes to talk to each one. Frank has an alibi, but Nate does not, although he does have an explanation of where he was that night. Because Nate tries to run away and fires at Dillon while trying to escape, Dillon jails him and has him charged for the murder of the clerk.
The Cumbers family has this motto - "We take care of our own." What they really mean is that they punish wayward members of their family themselves and resent and are even shamed of the idea of the government stepping in and meting out punishment for crime.
So the obviously tragic thing about all of this is that none of the members of the Cumbers family talk to one another about what really happened that night. As a result they all come up with their own individual plan that results in a joint tragedy.
The not so obvious thing in this teleplay is that in the old west it was common for the frontiersmen to feel this way about the law interfering in a matter of justice. They felt that transgressions were a private matter, and that prison or a public hanging was how you dealt with the lower class who didn't have the discipline to "take care of their own". Over the years, you'll see this same attitude of feeling like Dillon is an interloper uttered by many a frontiersman. Realize this was not just the product of John Meston trying to come up with an interesting story.