Matt captures his prisoner, a man wanted for the murder of a fellow marshal, in the desert. They need to find water and all of the places Matt has tried are dry. He asks Lorca, who knows the country, to tell him where the water can be found. Lorca refuses to tell him. When threatened, the prisoner reveals that there is a watering hole over the hills but it is controlled by the same rancher whose men he killed. Matt decides they have no choice but to risk it.
At the watering hole, Lorca asks where they're headed. Matt tells him they're going to Kansas City. The prisoner points out that they're not likely to make it without horses, to which Matt responds that he can likely find horses out there somewhere. The prisoner reminds him that they're headed into Tyson's country. Tyson will not supply horses to the one who murdered his men or to anyone trying to take that man in.
Before they can move on, three horses ride over the hill toward the watering hole. Lorca indicates these are Tyson's men. Matt moves himself and his prisoner toward cover and they camp in the evening. Lorca tells Matt that Tyson is the one who killed the other marshal.
Tyson's men attempt to ambush Matt and his prisoner but Matt hears them coming. In the ensuing shoot-out, one of the men badly wounds Lorca and Matt has to kill Tyson's brother. The two escape when Matt distracts the remaining gunmen by tossing a rock in the opposite direction from the one in which they flee.
Matt takes his Lorca down into the town controlled by Tyson and seeks a doctor to remove the bullet from his prisoner's arm. Lacey is sympathetic to their plight and agrees to shelter them and repair Lorca's arm.
The doctor suggests leaving Lorca for Tyson but Matt won't do it. He goes out into the town searching for horses to carry them to Kansas City. The man at the corral turns a shotgun on Matt and refuses to give him the the horses. Rather than harm an innocent man, Matt leaves without the horses.
When Matt returns to Lacey's, the doctor offers him the use of his horse and to fix them a meal before they leave. Matt tries to persuade the doctor to come along with them since Tyson will probably kill him for helping them, but Lacey refuses. Tyson and his men destroy his home when they find out but leave him alive.
A knock at the door interrupts their meal. Laurel, Tyson's daughter, offers them the use of two horses if he will take her with him. Matt refuses to take her but she loans him the horses anyway. Laurel leaves on her own horse, following Matt and his prisoner.
Laurel catches up to them and tells Matt to head north into the mountain country. She told her father to look for them in the south and when he finds out, he'll kill her. Matt takes Laurel along with them. When Lorca can no longer continue because of his wound, she leads them to a sheep herder's camp where he can rest.
With Tyson and his men closing in on them, Matt, Laurel, and Lorca ride out of the sheep herder's camp. Tyson and his men kill Changra after finding out he sheltered Matt and his prisoner.
The marshal, Laurel, and Lorca arrive in a small town with a train depot. Matt wants to catch the train when it stops to water. Lorca expresses the hope that Tyson gets there before the train so that Matt will have to kill the rancher. Lorca tells him that the men he killed came into his house, took his wife, and left her to die. When she died, Lorca tracked them down and killed them. Laurel verifies his story and says she will testify before a jury.
Tyson and his men ride into town and call the marshal out. Matt unshackles Lorca in order to give him a fair chance against Tyson and his men. Lorca tries to talk Matt out of facing Tyson but the marshal insists on doing his duty. The man who maintains the depot gives Matt a couple of loaded shotguns.
Matt steps out onto the street with one of the guns and warns Tyson that he's interfering with federal law. Tyson reaches for his Colt and says he's the only law that matters. Lauren rushes out to confront her father and reveals that he is one of the three men who helped kill Lorca's wife. Lorca grabs a shotgun and starts firing.
At the end of the gun battle, Tyson is dead and Lorca is dying. Matt shackles the remaining gunman to be taken to jail.