By C. Glen Bellamy

The jig is up. Ben Affleck has been ridiculed for long enough. The “Gigli” jokes aren’t funny anymore — and that’s presuming they were funny in the first place. Sure, even during his former A-list period, he was never that much of an actor, at least not as far as anyone could tell. After being unfairly crucified during his Jennifer Lopez phase — a bad career move or two turned into absurd and unnecessary mockery — he had two choices: fade into oblivion or reinvent himself altogether.

He’s taken the latter option, going behind the camera that made him a star and jumping into the director’s chair for “Gone Baby Gone,” an adaptation of “Mystic River” author Dennis Lehane’s novel. If Affleck’s big debut is any indication, the second career has major potential. (It remains to be seen whether his fellow punch line Jennifer Lopez — similarly forgotten in the last few years — can do the same. Perhaps, getting rid of that stupid three-letter nickname would be a good start.)

The project is the perfect move for a new director. He has a story already in place, set in the familiar setting of the cozy Boston neighborhoods where he grew up, and he’s surrounded himself with world-class veteran actors such as Ed Harris and Morgan Freeman who make his job easier. Affleck put himself in the perfect position. Of course, the story, setting and actors can’t do the work for him — he still has to make the movie. Much to the chagrin of Jay Leno’s lame-ass joke writers who would love nothing more than for Affleck to fail again, he thrives.

A little girl disappears. The story makes local headlines. The close-knit neighborhood is in a vengeful fit. The cops are on it, but they’ve got nothing so far. In an effective contrast to the cookie-cutter victims of other movies, the girl’s mother, Helene McCready (Amy Ryan) is largely unsympathetic. She’s a lifelong drug addict who got involved with the wrong people, putting her daughter, by proxy, in harm’s way. No wonder the little one got snatched up.

Helene’s brother and sister-in-law bring in a small-time private detective, Patrick Kenzie (Casey Affleck, in another tense, restrained performance), who hesitantly takes the case at the urging of his partner/girlfriend Angie Gennaro (Michelle Monaghan). Patrick is unsure at first, but gradually buries himself in the case — even when the truth seems to be clear, even when others have filed it away and moved on to the next kidnapping.

The story has been noted for its twists and turns, but that’s secondary, I think, to the acting and filmmaking that enhance those twists. Affleck crafts a dark, moody atmosphere that brings a delicate urgency to characters and their actions. The movie works not just because of plot. In fact, the script probably has one too many twists for its own good. At a certain point, plausibility begins to tip a bit. The tension with which the story is told makes its flaws forgivable, more or less.

The telling of “Gone Baby Gone” isn’t an easy trick. Everything is shrouded in moral ambiguity. Characters have to make key decisions for which there is no definitive answer. The choices they make — and the reasons for those choices — can be surprising. You have to strike the right chord, and for the most part, Affleck does it.

There are a few “first-time filmmaker” gaffes — an overdramatic extreme close-up of a character’s eyes just as he’s