Buck Taylor, who guest starred in this episode, previously worked with Buddy Ebsen in Drago (1971) (11/22/71) in which Ebsen played the title role of Drago . Both episodes involved talking someone out of committing murder for revenge. In this episode, Taylor was one of the would-be killers. In Drago, his character talked Ebsen out of committing murder for revenge.
It a little odd that when Barnaby arrives in the town Betty is staying in he doesn't recognize anything. Just two episodes before this was the same location he was stranded in while looking for the missing wife of his client. Presumably the two episodes were shot back-to-back to save money, and for some reason they failed to broadcast them months apart. The location is the small town of Piru, CA, located north of Los Angeles. This location was used repeatedly in Quinn Martin productions, including Cannon and The Fugitive, among others.
Drago was an episode of Gunsmoke.