Part 1: the Boys Who Escaped from Wolves (1975)

Mystic River opens in 1975 and introduces three young boys who are ten and eleven years old and live in East Buckingham, a working-class part of Boston. Two of the boys, Jimmy Marcus and Dave Boyle, live in the Flats area, while Sean Devine lives in the nicer Point area. Sean's father works as a foreman in a candy factory, where Jimmy's father is also employed. Dave tags along wherever Jimmy goes, including the Saturday visits that Jimmy and his father make to Sean and his father.

After an incident where Jimmy, the daredevil of the group, jumps onto the subway tracks to retrieve a lost ball and has to be dragged off the tracks,Sean's father tells Sean he can only play with Jimmy in front of their home. The next time Jimmy and Dave visit Sean's house, Jimmy is not...