If there's another turn by an actor this year as Oscar-worthy as that of Casey Affleck's in "Manchester by the Sea," I can't imagine it. As a man locked in non-negotiable remorse, Affleck delivers a portrait of such power and humanity it sticks with you weeks after viewing the film.

"Manchester by the Sea," written and directed by Kenneth Lonergan -- a standout of this year's New York Film Festival at Lincoln Center -- got a lot of love earlier from Sundance. For me this raises alarms. Sundance sometimes glorifies navel-gazers that are too cute by half ("Little Miss Sunshine"). Or small gems that are just, well, small ("Napoleon Bonaparte") -- and add to that Lonergan's own "You Can Count On Me," despite its touching moments. "Manchester" knocked me sideways

In its bare bones, "Manchester" follows Boston janitor Lee Chandler (Affleck) as he returns to his former titular home on the New England coast after the death of his older brother (Kyle Chandler) from heart failure. Yes, it's the old chestnut of returning home after a family death, but Lonergan sidesteps any cliches. Lee's dismayed to learn he's been appointed by his brother's will to act as guardian to his teen-age nephew Patrick (a marvelous Lucas Hedges), a role for which he feels profoundly unsuited.

Flashbacks are interleaved -- often abruptly, as if Lee is more claimed by the past than the present -- with Lee's rocky new relationship with his teen aged nephew. We learn that at one time Lee had a wife (Michelle Williams), there were three children, a decent job, a community. Eventually, Lonergan tips into the narrative what went so terribly wrong in Lee's life to produce a man who connects with people only through bar brawls and has consigned himself to the dumpster.

The music cueing these crucial scenes is Lonergan's only misstep. Filmmakers, please, refrain from using that churchy, over-worked Albinoni piece (you know the one I mean) to signal pathos. Following the big reveal, the question hangs fire: can Lee redeem himself and find the way forward by playing surrogate dad to his vital young nephew? As spring reawakens the town, you can practically feel the audience leaning into that hope.

But Lonergan -- also a man of the theater and author of the hit play "This is Our Life" -- has little interest in stroking his viewers. Happily, the film's bleakness is relieved by comic byplay between Lee and his horndog nephew, who's juggling multiple girlfriends, and by the decency and community spirit of these salty-tongued New Englanders.

And by surpassingly fine acting. Affleck conveys decades of spiritual drift with recourse to little language, through screen magnetism alone. When he does speak in his trademark grainy drawl, you hang on every word. That mesmerizing voice has served to channel characters from an outlaw ("The Assassination of Jesse James"), to a doomed Clyde-style lover ("Ain't Them Bodies Saints"). Always the same (extremely sexy) drawl, yet every time it nails the character. In fact, from film to film, Affleck embodies the quintessentially American figure of the loner and outlaw. His third act encounter in "Manchester" with Michelle Williams, when she throws him a life line, is so raw, you're unsure what you've just seen. How many takes to get to that?

Interestingly, Lonergan, is part Irish, part Jewish, and must have inherited an overheated notion of original sin compounded by guilt. Manchester is imbued with the idea of sin, and asks whether for certain acts, however blundering, there exists no forgiveness.