Affleck brothers deliver the goods with 'Baby'

A decade ago Ben Affleck and Matt Damon won an Oscar for the screenplay for “Good Will Hunting.” Since then, Affleck — good at playing average Joes and as a supporting player — parlayed his Oscar notoriety into a misguided action-hero career.

Critics have loved to hate Affleck, and admittedly he has made it easy with one bad acting choice after another. Undoubtedly, the cynics were ready to pounce on “Gone Baby Gone,” Affleck’s directorial debut, but it may just prove to be his best career choice since he sat down to pen “Good Will Hunting” with buddy Matt.

“Gone Baby Gone” is based on a novel by Dennis Lehane, the author of 2003’s “Mystic River.” As with “Mystic River,” “Gone Baby Gone” is set in Boston and deals with the investigation of a tragedy involving a girl. In “River” it was a murder; in “Baby” it is an abduction.

“Mystic River” was heralded for its acting, with Sean Penn and Tim Robbins both winning Oscars, and, while their performances were excellent, it was the sort of acting that screamed acting. In contrast, “Gone Baby Gone’s” acting isn’t showy, but it feels far more authentic, and because of that the film may be even better than “Mystic River.”

In a case of nepotism gone right, Affleck casts his brother Casey as Patrick Kenzie, a private detective hired by the sister (Amy Madigan, “Field of Dreams”) of the missing girl’s mother (Amy Ryan, “Capote”). The local cops, including Morgan Freeman’s police chief and Ed Harris’ investigating detective, reluctantly let Patrick and his partner/girlfriend (Michelle Monaghan, “Mission Impossible 3”) help with the case.

Patrick, who spent his whole life in the same neighbor, has connections and knows how to get people to talk who refuse to talk to the police. As Patrick keeps digging, even after the police have stopped, he opens up an ethical can of worms that makes the film more than just another crime movie.

Ben as writer and director does an excellent job at capturing the atmosphere of the neighborhood. Ben grew up in Boston and shows a feel for the flow of speech that goes beyond the familiar heavy Bostonian accent. He gets the attitude right. Ben even manages to slide in some sly commentary on the symbiotic relationship between the media and the neighborhood.

It helps that much of the cast is populated with unknowns or character actors, especially in the case of Ryan as the drug addict mother of the missing girl. Ryan is completely convincing in a performance that doesn’t feel like you’re watching acting, but rather the real thing. Drug addicts on screen can become hammy and false, but Ryan sidesteps stereotypes. Her character isn’t a sympathetic one, but Ryan, at least for one scene, makes you believe this woman’s pain.

Casey has been bouncing around Hollywood for nearly as long as his brother, but almost always as a supporting player, with the most high profile example being the “Ocean’s” trilogy. Here, though, Casey really gets to shine. His work is introspective and understated.

It could be easy at first glance to dismiss his acting as flat, but there’s more going on here. There is a low-key charm paired with a quiet intensity. Casey’s Patrick is a pretty boy who is mockingly called Harry Potter. But his looks make him deceptively non-threatening, and Casey makes Patrick’s ability to talk to just about anyone whether cop or criminal plausible.

The veterans of the cast, Freeman and Harris, are reliably excellent. Freeman has played cops before, but here he manages to put a new spin on his traditional persona. Harris and Casey have an extended conversation about the morality of doing a wrong for a greater right that is dynamite. The scene as written is almost yelling: This is the film’s major conflict, but as acted by Harris and Casey it is hard to fault. They are near perfection.

And Ben’s direction throughout is crisp and smooth with time for characters to breathe and develop. Ben has a thing for shooting cloud-filled sunrises and sunsets that gives the film a certain beauty. There are some missteps — most notably a use of voiceover narration midway that feels clunky — but this is a strong film by any filmmaker, first time or otherwise.