At school, the self-assured Richard and introverted Justin do not associate with each other. But after hours, they have a twisted bond with one another that goes beyond a normal "best friend" relationship. With Richard an ace manipulator and Justin highly studied in forensic procedures, they make a plan to brutally murder a nameless face off the street and see if they can get away with it. Assigned to the case is skilled police detective Cassie Mayweather (Sandra Bullock) and rookie partner Sam Kennedy (Ben Chaplin). When all evidence points to high school janitor Ray (Chris Penn), Sam believes that the murder has been solved. Cassie is not so sure, however, growing more and more suspicious of Justin and Richard, whom she has a gut feeling are somehow involved. Meanwhile, in working on the case, Cassie is finally forced into facing a deep, dark secret from her own past.

"Murder By Numbers" is a skillfully woven motion picture that cuts back and forth between the individual stories of Cassie and Sam, and Richard and Justin, until they inevitably collide. About equal time is spent with all of these characters, each one a satisfyingly fleshed-out and wholly believable creation. Director Barbet Schroeder wisely does not treat Richard and Justin as one-dimensional villains, but paints them as humanistic, flawed, and dangerous. Likewise, the cryptic inner turmoil Cassie is going through is deliberately uncovered as the film progresses, deepening the difficult emotions that have built up inside her over the years.

Lead actor Sandra Bullock (2000's "Miss Congeniality"), who also executive produces, so often is viewed as a comedic actress that some viewers don't stop to realize what a focused and talented thespian she truly is. In the role of Cassie Mayweather, Bullock has encountered one of the darkest characters she has ever been asked to play, and she handles it with a seriousness and realism that seems genuine. As partner-turned-possible-love-interest Sam Kennedy, Ben Chaplin (2002's "Birthday Girl") is less notable, if only because his character seems like more of a device to aid Cassie in her personal self-discovery.

As good as Bullock is, fresh young actors Ryan Gosling (2000's "Remember the Titans") and Michael Pitt (2001's "Hedwig and the Angry Inch") steal the show as Richard and Justin. Both Gosling and Pitt have the demure, sophistication, and overwhelming screen presence of an actor twice their age. They sink into their collective roles, too, with Gosling making Richard a forcefully alluring and calm psychotic, and Pitt turning Justin into a young man who, for all of his intelligence, fails to recognize the horrible choices he makes before it is too late. Most intriguingly of all, Richard and Justin are portrayed as otherwise normal high school seniors who have fallen to the wayside due to unsatisfying home lives and wealthy, uninvolved parents.

Unlike the recent Jodie Foster suspenser "Panic Room," "Murder By Numbers" moves at a purposefully slow pace that draws the viewer into the plot and characters, gets them to care about their fates, and then leads them to a thought-provoking finale that packs a wallop. While the film doesn't always surprise with its story developments, some of which can admittedly be telegraphed in advance, it is never anything less than a smart, thrilling, disturbing entertainment.