The show is remade as a western. Number Six is a sheriff who has turned in his badge and gun. He is kidnapped and dragged to the town of Harmony, where number two, as the Judge, asks him why he gave up his job and attempts to coerce him into working as sheriff of Harmony.
Throughout, Number Six refuses to take up arms, until the end, when Kathy, who has been promoted as a romantic interest for him, has been killed. He then shoots her murderer (the Kid, the Judge's chief enforcer) and confronts the Judge. He kills the Judge's henchmen, but is himself shot by the Judge.
He falls to the ground, then comes to--still in the saloon, but wearing his usual clothing, and alone except for cardboard cutouts of people and animals. He walks a short distance and finds himself in the village.
It is revealed that the episode was a directed hallucination: Number Six had been drugged and put under pressure to try to get him to crack. The plan failed, of course. Number Twenty-Two, who played Kathy, leaves in distress, and goes to the mock western town. There, she encounters Number Eight, who played the kid, and discovers that he is mad: he strangles her, as he did in the hallucination. Number Six arrives too late to stop him, and when Number Two arrives, Number Eight throws himself from a balcony.
So much good all this did them.
Notes
Trek also did a western-style episode in the third season, Spectre of the Gun, but it was not so good.
This episode does a good job of tying the events in the hallucination to the rest of the show. The general relationships between the characters is reproduced. The level of overt violence is increased, but there was always the threat of violence behind events. And there are little touches, like the green check pattern on the sheriff's window, which are nice to see.