Inspirational teacher who's hooked on crack

It doesn't take long to get pulled into Ryan Gosling's work as Dan Dunne in Half Nelson.

By the time he has stumbled out of bed (a mattress on the floor) and foraged around his grim New York City walk-up for something to feed the cat, the audience is there.

Looking half-dead and out of his head, "Mr. Dunne" walks into his eighth-grade history class and proceeds to engage his students - all black or Hispanic, all with other things on their minds - in a tricky discourse about opposing forces and social change. He makes them laugh. He makes them think.

And then he sneaks off to the gym to smoke some crack.

Half Nelson, a first film by director Ryan Fleck, who authored the screenplay with Anna Boden, is a showcase for Gosling, the young Canadian who played a self-loathing anti-Semite in The Believer and a troubled teenage killer in The United States of Leland. (He's also had more mainstream roles: in the love story The Notebook, as a football player in Remember the Titans.)

An inspirational teacher with a drug habit - it's a recipe for Giovanni Ribisi-ian overacting, but Gosling brings the character to life from the inside out, quietly, watchfully. It's a performance that will make you cringe - with despair, with empathy - as Gosling's Dan takes one self-destructive step after another.

Managing to evade the easy tropes and templates of the dedicated-teacher-in-the-troubled-school genre, Half Nelson is a character study and a love story - a love story that ventures onto potentially dangerous ground. Mr. Dunne is discovered lighting up a vial of crack in the girls' bathroom by one of his students, Drey (Shareeka Epps). A lonely kid whose brother is in prison, whose father is long gone, whose mother works double-shifts, and whose "uncle" is a dealer in her Brooklyn neighborhood, Drey doesn't rat on her teacher - she befriends him.

So begins a relationship that is, at turns, that of a mentor and his protege, of a guardian angel and her wayward charge, and of codependents pushing themselves toward all kinds of disaster.

Half Nelson isn't perfect. A third-act scene with Dan going home to visit his family sketches his pathology in simplistic brush strokes (oh, Dad's a drunk, and Mom's a do-gooder-turned-cynic). The ex-girlfriend (Tina Holmes) who has gone through rehab and now sports an engagement ring shows up to remind Dan (and us) of the road not taken - and the one that should have been. And the ways in which Dan's world intersects with Drey's in the weed-strewn lots and ugly motels of the outer boroughs stretch credulity.

But Gosling anchors the picture, and Epps (who had the same part, as Drey, in Fleck and Boden's short run-through for this story, 2004's Gowanus, Brooklyn) has a kind of grace, presence and knowingness that far more experienced actors struggle vainly to find.

Contact movie critic Steven Rea at 215-854-5629 or srea@phillynews.com. Read his recent work at http://go.philly.com/stevenrea.

Half Nelson *** (out of four stars)

Produced by Anna Boden, Ryan Fleck, Jamie Patricof, Alex Orlovsky, Lynette Howell and Rosanne Korenberg, directed by Fleck, written by Boden and Fleck, photography by Andrij Parekh, music by Broken Social Scene, distributed by ThinkFilm.

Running time: 1 hour, 46 mins.

Dan Dunne. . . Ryan Gosling

Drey. . . Shareeka Epps

Rachel. . . Tina Holmes

Isabel. . . Monique Curnen

Frank. . . Anthony Mackie

Parent's guide: R (sex, drugs, violence, profanity, adult themes)

Playing at: Ritz Five, Ritz Sixteen/NJ