A 17-year-old New York City high-school student (Anna Paquin) feels certain that she inadvertently played a role in a traffic accident that has claimed a woman's life. In her attempts to set things right she meets with opposition at every step. Torn apart with frustration, she begins emotionally brutalising her family, her friends, her teachers, and most of all, herself. She has been confronted quite unexpectedly with a basic truth: that her youthful ideals are on a collision course against the realities and compromises of the adult world.

An above-average study of grief.

There have numerous, juicily entertaining stories published about the long-delayed drama Margaret. Written and directed by Kenneth Lonergan (You Can Count on Me, writer of Scorsese’s Gangs of New York), it was shot in New York City late in 2005, and has sat in an existential limbo until recently. The various causes take in the legal, moral and aesthetic, but it doesn’t really matter anymore, because now that the film is slowly being released it’s clear that Margaret is a fascinating, ambitious work. It has failings, but they’re not fundamental, and if anything they speak to just how much Lonergan tried to coerce into a single story. He was aiming for ecstatic transcendence.

Lonergan is attempting to address the emotional state of post-9/11 New York City

Lisa Cohen (Anna Paquin) is a smart, vituperative private high school student on New York’s Upper West Side whose segue into adulthood is not going to be easy. 'Is that a real question or a Lisa question?" replies one of her teachers, Mr. Aaron (Matt Damon), when she queries him in a way meant to test his own self-assurance. Lisa is not sure who she is, but her options are dramatically changed when she playfully distracts a bus driver, Maretti (Mark Ruffalo), who then accidentally runs a red light and kills a female pedestrian (Alison Janney).

Lisa tells police investigators that the light was green, and like much of what she does in this often bracing movie it’s not clear whether she trying to do what she believes is right or is creating a situation to insert her own psyche into. Her misdirection begins to slowly gnaw at the teenager, and as the film unfolds it becomes apparent that Lonergan is attempting to address the emotional state of post-9/11 New York City in the form of a single, increasingly tormented soul.

Margaret runs for two and a half hours – a legally agreed upon limit – and within that time Lonergan keeps digging down further into Lisa’s motivations while sketching the world around her. Lisa’s mother, Joan (J. Smith-Cameron), is a Broadway actress just starting a hit show, and Lonergan counterpoints the performances the mother gives with those of the daughter. But at the same time he has Joan being courted by a Columbian businessman, Ramon (Jean Reno), in one of the several strands that could have done with detail to render it fulfilling.

Anna Paquin played a similar character – the dangerously inquisitive private school student – in a key post-9/11 movie, Spike Lee’s 25th Hour, and a decade after that painfully inspired tale was released Margaret feels like a bookend to the era it began. Here, however, Paquin’s Lisa is central, and it’s a coming of age tale where she increasingly inserts into the lives of those around her, whether visiting Maretti at his home or seeking out the victim’s best friend, Emily (Jeannie Berlin), to see if they can take legal action to retrospectively punish the wayward driver.

Paquin’s vision of youth is wayward and all-encompassing – at one point she’s losing her virginity to the laidback Paul (Kieran Culkin), the next she’s antagonising those around her with assumptions about her place in their lives. Lonergan stretches so much out to give you her emotional texture, whether it’s the bloody final minutes of Janney’s pedestrian or the schoolroom debates over fundamentalism and perceptions of Islam and Israel.

Lonergan himself appears, as Lisa’s absent father who lives on a Californian beach and may well be a writer who has relocated to Hollywood, and it’s clear that the filmmaker identifies with his fictional child. He wants to capture everything he can about Lisa, and match it to the moods and the feels of a wounded city, and if he doesn’t have the technique to always make that happen, then he undoubtedly can write individual scenes that dig deeper and more painfully into these lives than you would hope for or expect.

There is a long scene between Lisa and Jeannie that proceeds from cloying caginess and insincerity to raging confrontation, and it’s one of the most of the powerful pieces of drama seen on the screen this decade. The take is both lacerating and somehow liberating, and it’s more than enough that Lonergan could find his way to it without being able to condense so much else into a manageable movie. Margaret is flawed, but certainly no failure.