Just outside the small town of Pauley, a Native American woman is attacked by two riders on horseback, raped, and killed. Her husband, Matt Morgan (Kirk Douglas), the town marshal, has only two clues to their identity, a fancy saddle with the initials "C.B." that one of the men left behind, and the fact that his wife cut one of the two men deep across the cheek with a buggy whip. Morgan traces the saddle to Craig Belden (Anthony Quinn), an old friend and now a wealthy rancher in the town of Gun Hill, but he knows Belden well enough to know that he couldn't have had anything to do with attacking his wife. Morgan's arrival with Belden's saddle sets off ugly rumblings in Gun Hill, and when he confronts the rancher, he discovers that it was his son Rick (Earl Holliman) who had his horse and the saddle, and rode out with a cowhand friend of his, Lee (Brian G. Hutton) -- but they claim their horses were stolen. Belden tries to convince Morgan, and wants to believe himself that whoever stole the horses must have killed his wife, but when Morgan mentions the cut that one of the killers will have on his face, they both know the truth. He vows to take Rick and Lee back to Pauley to stand trial, while Belden swears he'll do anything it takes to protect his son. Belden is virtually all the law there is in Gun Hill -- the sheriff (Walter Sande) won't help Morgan serve his arrest warrants on the two men, or even let him use the jail to hold them until the last train that night; there's not a working man, a shopkeeper, or even a prostitute in the whole town that will go against the rancher, and Belden's foreman Beero (Brad Dexter) and his men will strongarm anyone who might start feeling brave. Only Linda (Carolyn Jones), a woman who has been both romanced and abused by Belden, will lift a finger on Morgan's behalf. The marshal is nothing if not resourceful, however, and Rick Belden is also too stupid for his own good, and manages to fall into Morgan's hands in short order. Very quickly, a standoff ensues, with Morgan holding Rick in one of Belden's buildings against virtually the entire town, while the deadline -- the last train out of Gun Hill that night -- approaches. People die and a chunk of Belden's holdings are destroyed, but Morgan is about to get Rick onto the train and off to trial when suddenly, one sudden act of violence destroys father and son in a matter of seconds.