Fifteen years ago, wealthy but crippled Colorado cattleman Arch Strobie (Ray Collins), whose own son Lee (Robert Walker) was wild, took in young Owen Daybright (Burt Lancaster) as a foster son to help raise and control Lee. Now Owen is ranch foreman, but Lee, despite being married to Jen (Joanne Dru), is wilder than ever.
Unmarried Lily Fasken (Sally Forrest) gives birth but refuses to identify the father. After Owen gives Lily $500 to help care for the baby, her brothers Hub (John Ireland) and Dick (Hugh O’Brian) believe that he is the guilty party, but they are unaware that Owen has done this on Lee’s behalf. The brothers try to beat up Owen and he lodges a complaint against them. Sentenced to a week in jail, they vow to get even as soon as they’re out.
When Arch chides Lee for overdrawing his bank account by withdrawing $500 in gold, Jen realizes that Lee fathered Lily’s baby. She confronts him and Lee tries to lie his way out. She decides to leave him but is persuaded by Owen and Arch to stay. Lee inveigles Arch to make him a partner in the ranch by saying that he will strike out on his own unless he gets a half-interest; he gets what he wants and learns that the other half will go to Owen, once Arch retires or dies.
Jen locks Lee out of their bedroom. He gets drunk, mistakenly believing she and Owen are carrying on behind his back. He schemes to get rid of Owen and make a fortune at the same time by conspiring with Hub and Dick to ambush Owen during the spring cattle roundup. On the trail, Lee secretly sells 3,000 head of the cattle, intending to run off with it, but Owen learns of the plan.
Lee pretends to change his mind. He persuades Owen to ride in with him to stop the sale, but in fact he lures Owen into a trap. Hub and Dick, waiting in ambush, wound Owen as Lee casually rides away. In the ensuing gunfight, Owen Kills Dick. Hearing shots, a group of trailhands ride to Owen’s rescue. They chase down and shoot Hub. Owen catches up with Lee and tells him that they are both going to confess everything to Arch. Lee refuses and draws his gun, forcing Owen to kill him. Owen breaks the news to Arch and Jen.
By Richard Thorpe (https://archive.org/details/VengeanceValley) [Public domain], via Wikimedia Commons