Henry Fonda's character is one man who believes in capital punishment, but also believes in the right to a fair trial. However, he faces down a large posse of bloodlusting men who are not interested in examining the difficult truth, but instead who prefer the convenient satiation of their rage. How does one voice among many speak, especially if they don't want to hear? There is a depth to it, similar to "Twelve Angry Men," also starring Fonda.
Anthony Quinn is one of two men facing a tree-hung noose. MASH's Henry Morgan is very young and dapper here (without his horse, Sophie), and stars as Fonda's friend.
A subplot regards a military leader who essentially leads the posse to the men, and his relationship with his son whom he forces to come along. The son, a prim and delicate sophisticate is opposed to his machismo-laden father in both personality and mission. Their conflict between right and wrong, son against father, man against child is more than a subplot, but a natural part of any such confrontation.
A short film of 75 minutes apparently not yet on DVD, it is acclaimed as a classic. However, it is far from showing the powerful vistas of "Red River" or the gruff but witty one-liners of "The Good, the Bad and the Ugly." It moves quickly, and its tight editing avoids cliches and limits the viewer from feeling as if he can expect the next line.
I fully recommend "The Ox-Bow Incident." It is the sort of movie worth watching in a high school civics course, or in a movie discussion group.