What happen to Lucas McCain son on the rifleman?

In the television series "The Rifleman," Lucas McCain's son, Mark, faces various challenges throughout the show, but one of the more significant events occurs in the episode titled "The Man from Salinas." In this episode, Mark is kidnapped by a group of outlaws, leading to a tense rescue by Lucas. Overall, the series often emphasizes the father-son bond and their adventures in the Old West.