In a small town in Arizona, young Scott works as a street cleaner who is just waiting for the opportunity to escape from his humble job in order to demonstrate his true value to everyone. An aged but experienced gunman, Talby, arrives in town and takes the young man under his wing. He teaches him all the tricks of the trade and in a very short time Scott becomes as efficient as his master. Talby, together with friends, takes control of the town, and does not hesitate to shoot the old sheriff. The sheriff, however, was an old friend of Scott's, who subsequently declares war on his mentor and his band of outlaws, which he consequently kills. In the final decisive duel, Scott kills Talby, but his is a bitter victory.

Giuliano Gemma plays the rather strange character of Scott, a social misfit who has never known his father, ill treated and isolated by the community in which he lives. The father/son relationship which grows between him and the aged gunman (Lee Van Cleef) is extremely touching even if the latter is to reveal himself to be a poor example. It is interesting to observe the contrast between Lee Van Cleef's character and the old sheriff, another symbolic father figure for the restless Scott, to whom he gives the mythical Doc Holliday's gun with which he will then kill Talby. The concluding scene with the final showdown is ironically mocking, with Scott using the "commandments" once taught to him by his "teacher" to in fact defeat this latter's gang. The final scene is particularly moving, with our young gunman, after having had no choice but to kill his father figure / teacher, throwing away the gun in a fit of painful anger.