Jimmy (Sean Penn), Dave (Tim Robbins), and Sean (Kevin Bacon) are former childhood buddies whose friendship drifted apart the day Dave was abducted before Jimmy and Sean's eyes by a pair of child molesters. They are unexpectedly brought back together when another tragedy hits their Boston neighborhood: Jimmy's beloved 19-year-old daughter, Katie (Emmy Rossum), is found murdered in a park, and police detective Sean is assigned to the case. Meanwhile, the emotionally afflicted Dave becomes a prime suspect after coming home to his frightened wife, Celeste (Marcia Gay Harden), with blood on his hands and a story about a mugger that doesn't check out. As Sean's investigation leads him more toward Katie's boyfriend (Tom Guiry), Jimmy decides to deal out his own brand of vengeance.

"Mystic River" has a gangbusters opening thirty minutes as it astonishingly delves the viewer headfirst into the three old friends' lives, their past together, and the fully realized Boston setting that surrounds them. What begins with assured creativity and depth slowly loses its ambition the second that Katie's body is discovered and Jimmy sets out to find a suspect and a motive. With those promises it held also escapes the chance for an emphatic study of the human condition, wavering instead toward basic whodunit conventions with a maddeningly simple and unfulfilling denouement.

The editing by Clint Eastwood regular Joel Cox (1999's "True Crime") is confusing and hopeless, although it is difficult to say if it is the fault of Cox or simply screenwriter Brian Helgeland's inabilities. Major characters come in and out of scenes at random, sometimes disappearing for inordinately long stretches of time, while the movie's present-day time frame is negligible. In a brief scene midway through, Jimmy goes to the funeral home to prepare his daughter's funeral arrangements and obituary. By the time the conclusion has arrived and countless plot revelations have come to pass, there is still nary a sign of the actual funeral. This sloppy handling of the picture's movement through time distracts from the story when the viewer should be more concerned about the people involved.

With a few key exceptions, the actors do not get a chance to show off their best work here, not aided by occasionally foggy character motivation. In one of his most penetratingly effective performances ever, Tim Robbins (2002's "The Truth About Charlie") is flawless as the quickly unraveling Dave, who has never been able to escape the demons from his childhood. Even as Dave becomes a suspect in the movie's key murder, Robbins sees to it that he remains an empathetic individual and one whose actionswhatever they may behave an offbeat reasoning to them. As Dave's wife, Celeste, who is torn between staying faithful to her husband and doing what is right, Marcia Gay Harden (2002's "Casa de los Babys") turns in another exquisite supporting performance, poignant and seemingly more developed than she actually is. Harden's every moment, no less than in a heartbreaking confession she makes to Jimmy, astounds.

All other performances are either burdened by their own histrionics or the boundaries of the written page. As Jimmy, an ex-con who has his most cherished achievementhis oldest daughterprematurely taken from him, the usually fine Sean Penn (2001's "I Am Sam") falls into the former category. Penn, who has a knack for finding the truth in his every onscreen moment, is unusually off his game, overacting to the point of convolution in some scenes and underplaying others with a hollow ineffectiveness. Kevin Bacon's (2000's "Hollow Man") Sean, whose romantic subplot is outrageously flat and pointless, is notably less developed than his two leading male counterparts. As Sean's partner, Whitey, and Jimmy's goal-oriented wife, Annabeth, Laurence Fishburne (2003's "The Matrix Reloaded") and Laura Linney (2003's "The Life of David Gale") remain enigmas. In Linney's case, she is so lacking in screen time and depth that a climactic monologue she gives feels awkward and its intended emotional wallop hits the ground with a thud.

The setup of "Mystic River" promises far more complexity and narrative intrigue than what the viewer ultimately gets. The film's portrayal of the untimely loss of a child holds no real insights or power (instead, see 2002's "Moonlight Mile"), its revenge plot is unsatisfying and exploitive (instead, try 1996's underappreciated "Eye for an Eye"), and the character motivations connected to Katie and her murder are simply far-fetched. The final two scenes are especially problematic, seemingly adding more story threads when things are just wrapping up and leaving other characters open-ended. With "Mystic River," director Clint Eastwood has attempted to weave a detailed and lyrical tapestry of characters affected by the cruel hands of their own fates. Unfortunately, the finished product plays like a rough cut, severely muddled and with a core more empty than full.