Whether by choice or by circumstance, Casey Affleck has skirted the edges of stardom for nearly a decade since his breakout role in The Assassination of Jesse James by the Coward Robert Ford. Manchester by the Sea – a brittle, bruising drama that unfurls with the rhythm and humour of everyday life – marks a breakthrough for not just Affleck but his young co-star Lucas Hedges and beleagured director Kenneth Lonergan as well. It’s a triumph on a number of fronts, reaffirming the notion that complex, emotionally wrought dramas can still make their way to the screen unscathed.

Casey Affleck plays Lee Chandler, a gruff superintendent toiling away in wintry New England. By day he (barely) puts up with tenants’ endless compaints and by night he drinks his earnings away, occasionally picking ill-advised fights. His world-weary exterior and isolation obviously hide deeper wounds, and a loose thread is pulled from his fraying life when he gets a phone call telling him his brother Joe (Kyle Chandler) has died. Lee’s forced to return to his titular hometown of Manchester-by-the-Sea to wrap up his late sibling’s affairs and confront a life he’d left behind.

Once there, Lee reunites with his 16-year-old nephew Patrick (Lucas Hedges) and is shocked to discover that he’s now the boy’s guardian as per Joe’s will. They strike an odd couple – Lee’s slumped-shoulder sullenness against Patrick’s talkative charm. Hedges is the breakout here, playing Patrick as a well-adjusted and popular teen that’s struck down by his father’s death but still trying to move forward. Lee’s grief is internal and rarely given time to surface, and Patrick, though more verbose, often reacts similarly.

Small moments become gut-wreching in their simplicity, whether it’s Lee taking Patrick to see his father’s body or Patrick’s panic attack upon realizing the weight of what’s happened. What lightens the nearly two-and-a-half movie is the frankness of its New England characters and setting, with Patrick especially getting the lion’s share of the best lines. This is a movie about grief and how it flows from one family member to another, but it’s also about how to persevere or at least exist in the face of it.

That matter of factness about death and the mundane details surrounding it mean that the movie draws in viewers with its humour and well-realized world before dropping the hammer in a few moments of nearly unbearable and operatic intensity. When Lee’s prior tragedy is revealed it’s full of unimaginable sadness and writer/director  Kenneth Lonergan, who up until that point had shown a simple workmanlike directorial style, drives these scenes home with the force of a thousand hammers.

But moments like that wouldn’t work without levity, and Manchester by the Sea is full of it. Whether it’s Patrick juggling two girlfriends or Lee awkwardly avoiding the advances of single mothers, there’s a naturalness at play here that’s amplified by well drawn characters. A flashback structure allows Lonergan to withhold key details for maximum impact, but it also means that characters like Kyle Chandler’s Joe get fleshed out. And Michelle Williams, as Lee’s ex-wife, appears in only a few scenes but makes the most of her screentime, delivering a highly-pitched monologue that leaves things both said and unsaid, devastating Lee and the audience in the process.

So yeah, it can be a heavy film and all throughout it walks a knife’s edge of tragedy and comedy. The frisson between the two means that both are that much more effective due to the contrast. The night is always darkest before the dawn, etc., etc. That doesn’t mean that Lonergan hits upon easy answers though, and in fact his reticence to play into audience expectations lends the movie additional power. Lonergan’s background as a playwright also means that the attention to character and dialogue are nearly unparalleled in any other movie released this year.

When Patrick’s estranged mother – a former alcoholic who’s been out of life for years – gets back in touch with an offer of lunch as peace offering Lee sees a way out of his responsibilities. The ensuing meeting is horrifically awkward and shows that years of hurt can’t be swept under the rug, as the characters and audience are denied easy answers. There’s an outcome that clearly makes the most sense for Lee and Patrick, but the question is whether Lee can make amends with his broken self.

The hurt the characters experience is inherited – passed from father to son, uncle to nephew. In that way it’s a circle, and the movie is more than a little Catholic in its imagery, setting and motifs. Despite that possible heavy-handedness and a soundtrack of swelling classical, Manchester by the Sea remains as grounded as its working class characters. At the centre lies Casey Affleck in a remarkable performance that’s not showy buy truly revelatory, playing Lee as a tightly-coiled ball of sadness and humanity. Be prepared to watch the movie with a lump in your throat, punctuated by cathartic laughter. Time will tell how it ranks in the pantheon of greats, but for now Manchester by the Sea certainly feels like a new American masterpiece.

Manchester by the Sea (2016)

Directed by Kenneth Lonergan

Runtime: 137 minutes