At the center of Lonergan's opus is a young heroine that, in classic opera tradition, is wrestling with great tragedy. Her name is Lisa (Anna Paquin) and she's a familiar New York type -- the privileged, precocious Upper West Sider who attends a tony private school and forever acts as if she's older than her years. (It's probably worth mentioning up front that, despite the title, there's not a "Margaret" to be found in the movie. The name is borrowed from a 19th century poem that one of Lisa's teachers reads to her class.) Walking through her neighborhood one afternoon after school, she spots a bus driver (Mark Ruffalo) sporting a cowboy hat -- the very kind she's looking to add to her own wardrobe. Sprinting alongside the bus as it rumbles down the street, she successfully catches the guy's attention. Distracted, the driver doesn't notice the red light ahead of him and consequently runs over a woman crossing the street, severing her leg. What follows is the movie's single-best sequence, a nearly ten-minute scene where Lisa holds the dying victim (played memorably by Allison Janney) in her arms as her life slowly seeps away. Returning home still covered in the woman's blood, Lisa showers, changes and heads out to meet the cute boy that awkwardly asked her out on a date earlier that day, reassuring her mother (J. Smith-Cameron) that she's perfectly okay.

Naturally, it soon becomes apparent that Lisa is not okay. In the days following the accident, she increasingly begins to act out of character, picking fights with Mom, loudly denouncing a classmate who offers a mild defense of the Middle East (remember, Margaret was filmed in 2005, four years after 9/11 and the impact of the attacks reverberates throughout the movie), experimenting with drugs and calling up a slacker kid (Kieran Culkin) she barely knows and invites him over to take her virginity. (Their resulting sexual encounter is another standout sequence and may very well be the most awkward deflowering ever committed to celluloid. It's all the more amusing when you compare it to the naked acrobatics that Paquin now gets into week in and week out on True Blood.) And after initially lying to the police about the bus driver's culpability in the accident -- she told the officers that the light was green, not red out of some desire to protect the poor guy's job -- she reverses course and works with the dead woman's best friend, Emily (Jeannie Berlin) to find a legal way to force the MTA to fire him.

Her zealousness to see the driver punished is motivated partly by her own guilt and partly by his refusal to acknowledge any wrongdoing (when she pays an unexpected visit to his Bay Ridge home, he all but throws her out), but it also speaks to something larger that's happening inside her as well. Being an active participant in this tragedy has granted her a certain degree of power over the adults around her that she enjoys exploiting. It's under the guise of grief and confusion, for example, that she's able to endear herself to her cute geometry teacher (Matt Damon), even inviting herself over to his home where she attempts to seduce him. Meanwhile, her connection to the dead woman allows her to "adopt" Emily as a kind of surrogate mother, to replace her actual mom that's distracted by the opening of her new play, as well as the new man in her life, Ramon (French actor Jean Reno, improbably cast as a Latin lothario). And then there's the driver, whose very future she feels she holds in her hands. To be clear, Lisa isn't a villain that deliberately wants to hurt the people around her; she's a young woman whose moral compass is spinning wildly around as she attempts to distinguish between what's right and just and what just feels good. In that way, Margaret captures the confusion of adolescence better than any movie or TV series out there right now. It's like what Gossip Girl might be if any of those pampered teen fem-bots had a soul.

I may be making Margaret sound like a more cohesive movie than it actually is. Mostly it feels as though Lonergan is on the cusp of something great throughout, only to let that breakthrough repeatedly slip away from him. For every scene that plays like gangbusters, there are a half-dozen others that flop around onscreen, dying a quiet death. The movie's contradictions are encapsulated in its lead actress's performance; sometimes Paquin is brilliant, reaching levels of emotion we've never seen from her before. Other times, she's a shrieking harridan that can barely keep a handle on her American accent. And yet, in the days since I've seen Margaret, I haven't been able to get the movie or Paquin's performance out of my mind. Like the final notes of an opera, the film lingers, inviting you back to explore its mysteries a second and even a third time.

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