Long ago, Jimmy Markum (SEAN PENN), Dave Boyle (TIM ROBBINS) and Sean Devine (KEVIN BACON) were best friends, hanging out and playing on the streets of Boston. Something bad then happened to Dave, an event that forever changed him and eventually sent all of them on their separate ways.
Now another event has occurred that brings them back together. To the horror of one-time hood and current convenience store owner Jimmy and his second wife, Annabeth (LAURA LINNEY), their 19-year-old daughter, Katie (EMMY ROSSUM), is found brutally murdered.
Sean and his Massachusetts State Police partner Whitey Powers (LAURENCE FISHBURNE) are the first detectives on the scene and set out to solve the case by interviewing various witnesses and potential suspects such as Katie's secret boyfriend, Brendan Harris (TOM GUIRY). As they do their job, Jimmy's criminal friends, the Savage Brothers (KEVIN CHAPMAN & ADAM NELSON), do their own sort of detective work, thug style.
And Dave's timid wife, Celeste (MARCIA GAY HARDEN), begins to question him and his behavior when he returns home on the night of the murder, covered in blood and claiming to have beaten off and possibly killed a mugger. As the events unfold and emotions rise to the boiling point, the three former friends are reunited in ways they never could have imagined.