Dave Harmon (Clint Walker) is a United States Marshall, who has been sent by the governor to the territory of Yuma. It seems that the law is not welcomed there. Every Marshall that’s been sent has been chased out. Harmon however, is a different story. Upon arriving, he encounters two drunks and asks them to come with him to cool off. However, one of them pulls a gun on him and shoots. Harmon reacts and shoots him. That’s when Harmon’s problems really begin. He is told that the man he killed is the brother of Arch King, a powerful man, who adheres to only one law, his own.