While being transported from Yuma Prison, seven desperate men on their way to the gallows escape the prison wagon in North Fork, and one is seeking revenge on Lucas McCain after Lucas hits him for grabbing Mark.
From "The Rifleman Episode Guide List"
Those seven prisoners knew of that ploy to gain release because it had happened before back in late 1871. (The incident was depicted in "The Rattlesnake Brigade", an episode of 'Bonanza'.)
Outside the box, the 'Bonanza' episode aired after 'The Rifleman' episode, but on the Toobworld timeline, it occurred first.