Gunsmoke (1947)

Rancher Marlowe is shot in the back and killed by gunslinger Dirk Mattson. His son Brad, despite the pleas of his young sister Ginny, sets out for revenge. He and Dirk have a shoot-out in Helldorado and Dirk is killed. Brad is wounded and is being pursued by a posse, and passes out in the desert where he is found by Carol Henderson. She treats his wounds and rides for help to an outlaw camp where she and her father are being held captive. She persuades two of the outlaws, Billy and Shorty, to bring Brad to her cabin while he recovers. The camp is that of an outfit known as Duke's Raiders, a Nevada outlaw gang led by Duke Mattson, twin brother of Dirk. After a fight, Duke, not knowing that Brad killed his brother, asks him to join the gang. Brad agrees so that he can work from the inside and put an end to the gang.