The "Silver Kid" is an orphan who is deputized by the marshal of Silver City to help rid the town of a gang of gold mine claim-jumpers who will kill anyone who stands in their way.

In the West during the late 1800s, the vicious Jeffers gang murders local miners and steals their claims for resale. One of their victims is the father of Luke Cromwell, and although the gang flees when Luke appears, he shoots one of their men and discovers their telltale eagle medallion around his neck. Weeks later, when the gang attacks miners around Silver City, Marshal Lightning Tyrone, so named for his quick draw, organizes a posse to hunt them down. Young "Jane" Dusty Fargo sees Lightning off lovingly, while Johnny Sombrero, a ruffian known for shooting men in the back, is happy to see him go. The posse finds the gang, but loses them after they shoot Lightning in the shoulder. As Lightning convalesces at the local Army hospital, he realizes with dismay that while he can still draw his gun, his trigger finger has been damaged. The first surviving witness to the Jeffers' violence finally is admitted to the hospital, but Opal Lacey, pretending to be a nurse, strangles the man to keep him from talking. Lightning, unknowing, is taken with Opal's beauty and is thrilled to discover after his release that she has moved to Silver City. He also finds out that his friend, Dan Musick, has been shot in the back. Lightning suspects the involvement of Johnny and his friend, Rat Face Blake, but Johnny claims to have been working for Opal's supposed brother, Rod Lacey, who is actually the leader of the Jeffers gang. Lacey vouches for Johnny, and Opal suggests that Luke, who has quickly made a name for himself in town as a gunman called "The Silver Kid," may be the murderer. Lightning questions Luke, but is impressed by him and, realizing that he needs backup to compensate for his injured hand, deputizes him. That night, Dusty is upset to hear that Lightning has a date with Opal, but is pleased by Luke's attentions. Later, as Lightning is leaving Opal's house, Luke saves him by shooting Rat Face, who was following Lacey's order to attack the marshal. After they identify the eagle medallion around Rat Face's neck, Lightning and Luke bring the criminal to a secret cave to prevent the gang from killing him to keep him quiet. The next night, Johnny stirs up a lynch mob to attack the jail, hoping to free Rat Face. As Lacey pretends to back Lightning, his men break into the jail and later report to Lacey and Opal that Rat Face was not there. That night, Opal, scheming to trick Lightning into revealing Rat Face's location, pretends that the Jeffers gang broke into her house and kidnapped Lacey, promising to exchange him for Rat Face. Luke does not trust Opal and so follows Lightning to her house. Lightning fires him for insulting Opal, and when Luke retorts that he knows that Lightning can no longer shoot, Opal decides to use the marshal's injury to her advantage. The next day, Johnny challenges Lightning to a duel, and although Dusty has almost managed to talk The Kid into staying in town, Lightning assumes Luke told Johnny about his finger and punches him. Forced to confront Johnny in the middle of town, Lightning faces sure death until Luke reappears and kills Johnny. Before he dies, Johnny reveals that it was Opal who had Dan shot and who told him about Lightning's hand. Lightning races to Opal's, where Luke bursts in to inform them that Dusty is bringing Rat Face to the gang in return for Lacey. Opal promises to lead them to the gang hideout if they will then let her go. At the hideout, meanwhile, the gang abducts Dusty when she arrives with Rat Face. Lacey sees Lightning's posse approaching with Opal in the lead and shoots her. In the ensuing gunfight, Luke bravely rescues Dusty as Lightning chases down Lacey. In the hills, the marshal tricks Lacey into stepping into the open, where Lightning shoots him with his left hand. The posse rounds up the gang as Dusty and Luke, now engaged, introduce themselves to each other by their real names.