Actually, maybe it's not fair to say that a desire to restart his career is why Affleck made the film, only that it should be one of the byproducts. There's certainly nothing desperate or calculating about the final product. This is a riveting mystery/thriller that warrants attention regardless of who made it, or why.
Affleck casts his brother Casey in the lead, a private investigator named Patrick Kenzie who has lived on the same Boston block his entire life. He and his girlfriend/business partner, Angie (Michelle Monaghan), mostly work low-profile cases like finding people who have skipped out on their jet-ski payments, so they're surprised when a woman approaches them wanting help finding her missing niece.
The woman is Beatrice McCready (Amy Madigan), and it's her husband's sister's kid that's gone missing. Patrick and Angie have seen the TV news reports about it. Whole neighborhood's out looking for her, poor thing, and of course the whole police force, too. Everyone knows, but no one likes to point out, that the more days that go by, the less the chances are of finding her alive.
Not usually their kind of case, but Patrick and Angie agree to do what they can to help anyway, maybe because of their personal connection to the neighborhood. As duly hired private investigators, they're entitled to cooperation from the police detectives, who in this case are a couple of hard-noses named Bressant (Ed Harris) and Poole (John Ashton). The cops soon grudgingly admit that Patrick's contacts can help, and the search is on.
The missing girl's mother, Helene (Amy Ryan), is strangely complacent with regard to her abducted child. She's not apathetic, exactly, just ... detached. She and little Amanda live in something approaching squalor, and Helene is known as a regular down at the Fillmore Lounge, where booze and cocaine are among her favorite menu items. Not exactly Mother of the Year material, but does it explain what happened to Amanda?
Affleck, who co-wrote the screenplay with Cambridge pal Aaron Stockard, was smart to choose a book set in his old stomping grounds. The film is rich with local color, from the slang to the thick Boston accents, and the crowd scenes and supporting roles are populated by real-looking (i.e., unattractive) people. Patrick's connections to the neighborhood feel authentic. It doesn't seem like an outrageous coincidence that he and Helene were in high school together. They're about the same age, and most of the people in their community have never lived anywhere else, so why shouldn't they have a vague past connection? Patrick went to school with everyone he runs into, or used to go out drinking with them, or dated their sisters. It gives the film a sense of place, a sense that this is happening to real people in a real community.
The story deepens, going beyond Amanda's disappearance and reaching into other crimes, with people's past and present secrets coming to light. Patrick, always on the defensive because of his baby face that makes him look younger than his 31 years (which lines up with Casey Affleck's real age), can be hotheaded at times, but he struggles to keep a firm grasp on what's right and wrong. Other characters see things in grayer shades. Detective Bressant, gradually befriending Patrick the P.I., says he's done things that were technically wrong but that ensured justice would be served. He sleeps with an easy conscience.
After playing small parts in big films (like the "Ocean's Eleven" series) and big parts in small films (like "Gerry"), Casey Affleck may have found his star-making role in "Gone Baby Gone." He has his brother's easy-going likability (without all the extracurricular tabloid baggage) and a seriousness that serves this character well as he believably plays up Patrick's moral quandaries.
Furthermore, Amy Ryan is a revelation as Helene, a character plucked straight from the streets and dropped into the movie. As Helene gradually transforms from neglectful parent to concerned mother, Ryan changes with her, her eyes slowly opening to the magnitude of what's happening. The film doesn't necessarily need Helene to be this fully developed as a character, and that makes Ryan's extra-mile performance all the more noteworthy.
But that's true of several other supporting characters, too. Morgan Freeman has a few scenes as a decorated police captain who lost a daughter himself years ago -- a complete cliché of a character, yet Freeman uses his considerable talent to make the man fresh and relatable. Look at Amy Madigan as Amanda's concerned aunt Bearice and Titus Welliver as Bea's husband, two characters who seem to have a relationship with each other that extends beyond what we see on the screen. They aren't just figures who serve a function in the plot: They're actual people, with histories and memories.
As the story gets seedier and the felonies more alarming, the film starts to lose some of its distinct Boston flavor and become a more generic crime thriller. It also suffers a bit by having perhaps one plot twist more than it ought to, straining credibility in what is otherwise a highly credible film. (I assume that's how Lehane's novel goes, too.) But none of this detracts much from the absorbing, carefully constructed movie -- a boon to the Affleck family and to moviegoers as well.