Rory O’ Shea (James McAvoy) is too smart, cool and funny for his own good. He’s that kind of kid we all wished for as our high school best friend—a ruthlessly funny anarchist who acts cool, dresses cool, doesn’t take s*&t and protects us at any cost. And most of all, he understands us.

Rory’s arrival is critical for lonely Michael Robertson (Michael Connolly), a wheelchair bound young man severely afflicted with cerebral palsy, whose speech is incomprehensible to everyone but Rory, who understands Michael’s speech with perfect clarity. He also understands that Michael, like himself—confined to a wheelchair with advanced muscular dystrophy—is ready for a life outside the confines of the "system"—a special home for the disabled, regulated with a not so iron fist by Eileen (exasperated matron Brenda Fricker).

Rebellious Rory opens up shy Michael’s world to pubs, girls and the excitement of a two-bedroom flat. The catch? They both need constant care—they can’t even eat or bathe themselves, with Rory paralyzed from the neck down and Michael all tics and jerks, uncontrollable fits and slurred speech. His heart, however, is fine and beating for young live-in caretaker, Siobahn (Romola Garai). Soon he faces first love while Rory hits the lows of depression. Siobahn is caught in the escalating predicament as their idealistic independence clashes with difficult reality.

Both actors do very capable work and steer the film, for most of its running time, into unpredictable comic and dramatic territory. There’s more going on here than just their physical bodies not working—withdrawn Michael has a successful father who has disowned him, while Rory suffers from manic depression yet still fancies himself an average young dude into women, beer and loud music.

Now to the young English actress Ms. Garai. Any actress who can make me regret missing "Dirty Dancing: Havana Nights," surely must be onto something. Though I overlooked her American debut in that superfluous picture, she first caught my attention as Reese Witherspoon’s best friend Amelia Sedley in Mira Nair’s "Vanity Fair" earlier this year. In "Rory O’ Shea," she’s the best thing in the film. She’s got a spark of sensual soulfulness in her direct and no-nonsense Siobahn. At first she appears a bottle-blonde mane with a touch of sarcasm, but then she makes you look a little deeper. She’s healthy-not an emaciated model type-and reminds one of a young Kate Winslet, full-figured and earthy, warm and not traditionally beautiful but so fresh and charming, throaty and almost sultry, that you can see why any man -- disability or not -- would fall for her.

Garai’s delicate scenes catering to needy Michael are some of the film’s best, even when the screenplay puts them through the familiar third-act treacle. She can feel Michael inching his way toward her, crossing what are, for him, profound new boundaries. But try as she might, the kid gloves come off when push comes to shove. As played by Garai in a performance that walks the line between compassion and the need to define what her relationship to Michael is-and-isn’t the character reveals some tricky and at times unintentionally hurtful dimensions. Spunky Siobahn is an original. Ditto Garai.

I could feel the film mechanically pushing my buttons through its climax, which is rushed and contains some squirm-worthy moments of calculated sentiment. Still, the film is worthwhile. It’s not a plea for acceptance or a cushy fable about how those with disabilities are so much better adjusted to life than the rest of us. It’s just a simple story about a human being’s need for independence and the search for identity. It makes some thoughtful points about the right to live without bureaucratic meddling. I just wish the film was more profound, had gone deeper and darker into Rory’s depressive highs and lows and Michael’s lovelorn melancholy. It doesn’t.