S9 E22: In the two-part series finale, Monica is up for career review and a possible promotion as she embarks upon what will become her very last and most challenging mission. As she journeys into Ascension, a town recovering from a tragedy, Monica encounters a mysterious drifter named Zack (guest star Scott Bairstow, "Wolf Lake"). When they arrive in town, they learn that a devastating accident had occurred there a year ago, killing almost all of Ascension's children and leaving behind a deeply scarred community. Zack is recognized from the day of the accident and suddenly the town has a focus for its anger. The townspeople quickly turn against him and demand that he be tried for the murder of their children.