In a multitude of ways, Joe’s arc in the “Blue Bloods” Season 11 finale resembles the story that has been told about his own father time and time again. Joseph Reagan is killed prior to the events of the series while undercover with a group of dirty cops called the Blue Templar. Despite advance knowledge that his cover has likely been blown, he continues to work on the mission until he is murdered by a fellow officer. Little more than a decade after his father’s untimely death, Joe faces an undeniably similar situation.
Throughout the finale, Joe focuses on taking down the criminal organization that he is placed undercover to investigate in the first place. At the end of Episode 15, the first of the two-part finale, it is revealed that a mole has been working inside the ATF, leading the NYPD to conclude that Joe must be pulled from the field. However, Joe is steadfast in his determination to remain undercover so long as his mission remains incomplete.
This leads the entire Reagan family to set out to bring Joe home safely by any means necessary, a mission which they ultimately succeed in. After Joe returns home, Frank offers Joe a compliment unlike any he has likely ever received before, saying, “Joe is truly his father’s son.” Joe’s journey is largely an effort to prove himself, not only to the rest of the NYPD, but also to the Reagan family as his father’s successor.