River of No Return (1954) on Netflix

Matt Calder, who lives on a remote farm with his young son Mark, helps two unexpected visitors who lose control of their raft on the nearby river. Harry Weston is a gambler by profession and he is racing to the nearest town to register a mining claim he has won in a poker game. His attractive wife Kay, a former saloon hall girl, is with him. When Calder refuses to let Weston have his only rifle and horse, he simply takes them leaving his wife behind. Unable to defend themselves against a likely Indian attack, Calder, his son and Kay Weston begin the treacherous journey down the river on the raft Weston left behind.