A stagecoach carrying lawyer Adam Stewart and his son Howie is held up by a group of masked bandits and taken to the small community of Ocatilla, Arizona. There Adam discovers the holdup was arranged by his brother John as a distinctive welcome to the formerly rough frontier. John then throws a party to introduce his family to his neighbors, including attractive widow Corinne Michaels, belligerent rancher Wick Campbell and his ward, young Maria Segura. John confides to Adam his dream to bring peace and law to Ocatilla after years of struggling to build a cattle ranch in the wild territory. John asks Adam to stay as the town's first lawyer, and his brother agrees despite Howie's reluctance. Later, when Howie shows an interest in Maria, Campbell takes offense, and John is forced to ask him to leave the party. At Campbell's home, Maria maintains she does not love him despite his strong feelings for her and runs away when Campbell tries to force himself on her. The following day, Campbell goes to the Stewart ranch looking for Maria, but John explains she is afraid of Campbell and he will offer her protection as long as she needs it. Furious, Campbell summons several gunslingers, led by Frank Scavo, to disrupt John's attempt to establish a law-abiding community. Campbell begins his terrorism by killing old rancher Tod Grinnel and making it look like self-defense. A few days later Campbell and his band stampede John's cattle and drive them to his ranch, where he mixes them with Grinnel's herd, re-brands them and takes them to market. When John reports to young Sheriff Clyde Gibbons and brings evidence of the trampling death of one of Campbell's men, Red Dawes, Campbell disavows knowledge of the rustling. Later at the saloon, one of Scavo's men, Dave Weed, tries to provoke a fight with an unarmed Howie. Scavo gives Howie his own gun, but to the men's surprise, despite entreating Weed not to fight, Howie kills him in self defense. Scavo and his men tell Clyde, however, that Howie instigated the fight and Howie is arrested. Angered over what he perceives as his father and John's acceptance of his imprisonment, Howie breaks out of jail and seeks out Maria for help. Both flee and Campbell is further outraged. John and Adam agree to go in search of the circuit judge to decide Howie's case, but Adam is caught by Campbell, who murders Adam when he refuses to reveal Howie and Maria's location. At Adam's funeral, Howie and Maria watch from a nearby hill and Howie vows revenge, despite Maria's pleas. In desperation, Maria brings John to Howie's hideout, and Howie blames his uncle for his father's murder. John returns to town and notes the arrival of more gunslingers and asks Scavo how to find Campbell. Scavo and another of his men, Al Drucker, try and trick John into a confrontation, but John kills Drucker and escapes. At Clyde's office, several townsmen gather to offer to help John fight Campbell and Scavo's gang. Corinne implores John not to resort to violence, so John tells them he will face Campbell alone. When Campbell and Scavo open fire on the sheriff's office, however, Corinne reluctantly gives the men her husband's rifles. Hearing the gunfire from his hideout, Howie braves the volley to join the men. After a barrage of gunfire, Campbell brings out Clyde's wife Marva as a hostage, and she exhorts the men to surrender. When a wounded Clyde considers it, Corinne defiantly goes outside to tell Marva that Campbell will never keep his word about letting the men live. Campbell then locks the two women in jail and, gathering dynamite from the town's small arsenal, begins tossing sticks at the sheriff's office. One man is killed and another, panicking at the explosions, runs out into the fire. When John and Clyde once again consider surrendering, Clyde's father deliberately stages a fatal diversion allowing the others to escape the burning building. Celebrating their victory, Scavo and his men take over the saloon, but Campbell tries to cut off their carousing. Scavo disarms Campbell, informing him that he and his men now run Ocatilla. Campbell finally learns of Maria's location, but when he arrives he finds John, who gives him a gun, then offers to accept his surrender. Campbell chooses the gun, but John kills him. John then returns to town, slips into the arsenal and attacks the saloon with dynamite, before discovering Scavo robbing the saloon safe. The two men fight viciously before a wall of the saloon collapses on Scavo. The rest of the gang is rounded up by Clyde and the townsmen, after which follows a double marriage ceremony of Howie and Maria and John and Corinne.
