A bunch of men kidnap Slocum and take him out of town to lynch him. Newspaper man Murdock hears what the men are planning and he sees them head out of town. He immediately runs into Wyatt's office to tell Wyatt what's happening, and Wyatt immediately grabs his shotgun and heads after the men. It's only been a couple minutes, and Wyatt should have caught up to the men, either before they got out of town, or just after. But it takes at least several minutes and by the time Wyatt catches up to them, they already have Slocum tied up, standing on a barrel, and ready to be hung.
During the trial, Wyatt comes into the courtroom and leaves the door open. There is no town outside. Just a wall, and the continuation of the courtroom floor. This has happened in at least one previous episode, when Wyatt's office door was opened wide. This is probably done so that all indoor scenes can be filmed at the studio, instead of at an outdoor filming location, in this case, the town setting.