The number in the "No. in series" column refers to the episode's number within the overall series, whereas the number in the "No. in season" column refers to the episode's number within this particular season. "Featured character(s)" refers to the character(s) whose back story is featured in the episode's flashbacks. "U.S. viewers (million)" refers to the number of viewers in the United States in millions who watched the episode as it was aired.