WARNING: SPOILERS

Kenneth Lonergan’s “Manchester By the Sea” unfolds slowly and naturally. It’s like life in that we make assumptions about the people we’re watching. It’s not like life in that we get to stick around to see how our assumptions are wrong.

Lee Chandler (Casey Affleck) is a handyman/super for four apartment buildings in Quincy, Mass., near Boston. He does his work calmly, competently, but with something missing, some spark. Early on, he seems to have the patience of Job. He shovels the sidewalks, fixes the drips, unclogs the toilets without complaint. At one point he overhears a tenant say she’s attracted to him, and she gives him a tip, but he doesn’t respond. Because he just unclogged her toilet and that’s no way to begin a relationship? Later, at a bar with a beer, he doesn’t respond to another woman’s flirtations. Then it’s near closing, he eyes two guys across the bar, and you think: Of course. He’s gay.

Then he picks a fight with the two guys. Turns out he’s not gay, not calm, doesn’t have the patience of Job.

Slowly, as he heads north to the titular town to deal with the sudden heart attack/death of his older brother, Joe (Kyle Chandler), we find out how he got this way.

At the local high school, he’s twice referred to as the Lee Chandler, and we wonder if he was a star athlete. Nope. When his brother’s will is read and he discovers he’s the guardian of 15-year-old Patrick (Lucas Hedges), he almost flips out. “I’m just a backup,” he says. Later, in flashback, we see him with a wife, Randi (Michelle Williams), and one ... two ... three kids? Really? So he doesn’t seem like a backup there. And hey, what happened to those kids anyway?

That, of course, turns out to be the answer to everything: Why Lee is living in a small, cramped basement apartment in Quincy, why he’s full of rage, why something is missing from him, why he can’t return to Manchester-By-the-Sea.

A few years ago I read a great piece by David Grann in The New Yorker about Cameron Todd Williams, a Texas man who was put to death for setting a fire that killed his wife and three girls—except he probably didn’t set that fire. The state of Texas probably executed an innocent man. I kept flashing to it, watching this movie, since Lee’s tragedy is similar. Drunk one night in a cold house, Lee starts a fire in the fireplace to warm up his girls, then walks down to the nearest convenience store to get more beer. When he returns his house is ablaze. His wife makes it out, his kids don’t.

The difference is that Lee isn’t charged with murder but wants to be. When the cops tell him he’s free to go, he tries to blow his brains out in the station. That’s why the basement apartment in Quincy. It’s his punishment, his prison. He’s doing life without parole. It’s also why he doesn’t want to leave—particularly for Manchester By the Sea, which just dredges everything up.

Thus the movie’s main conflict is set up: Lee, the new guardian, doesn’t want to stay in Manchester, but Patrick, with friends and girlfriends and school, and a father’s boat he wants to return to, doesn’t want to leave. Patrick has the better up-front argument, Lee the better buried argument. But even as this argument gets unburied, we see Lee making a go at it. We see him asking for work. We see him running into his ex. This is a powerful scene, and it also upends our assumptions. We expect that he’ll want forgiveness from Randi and she won’t give it. Instead, she has more than forgiveness; she has love. And he finds this unbearable. “No, you don’t understand,” he says, breaking away from her. “There’s nothing there.” Williams is so good in this one scene she might win an Oscar for it.

I still remember Roger Ebert’s review of “The World According to Garp.” Watching, he kept thinking, “This is nice ... this is nice  ... this is nice,” but for all of those nice scenes the movie never added up to anything meaningful. I think a lot of indie movies are like that. “Manchester” isn’t. All of its small scenes add up. The movie doesn’t give us a happy ending (as with studio films) or tragic ending (as with indies), but balances on that razor-thin line of honesty and understanding; of things that aren’t said and things that don’t need to be said. Its redemption is small, but more poignant for its smallness. For Christ’s sake, go see it.