Manchester by the Sea is the kind of movie wherein, the more one tries to excitedly talk about all of its best parts, the more it sounds like a suffocating nightmare. "It's such a great depiction of crippling guilt, like no other movie that I can think of! The main character is devoured by the most realistic, penetrating grief and self-hate this side of 1960s European art cinema! The scene where Casey Affleck and Michelle Williams are both wracked with emotional pain and have mutually incompatible needs to find their way out of that pain feels like having your guts kicked out of your body!" Kenneth Lonergan's third film as director (and sixth as writer) is also his third to depict the frustrating, painful process by which people find themselves incapable of rising above their past, but this time with tragic death.

What none of this suggests is how much of Manchester by the Sea is actually, like, watchable. It has a thoroughly unexpected streak of deadpan comedy to it, not nearly enough to make it "funny", not even to make it "not depressing". But comedy nonetheless, and very intelligently deployed comedy, at that. Not only does it let some oxygen into a movie that could very choke on its own sense of constant, dysfunctional misery, it also tells us quite a lot about the two main characters, and how they use jokes and deflection to keep the darkness at bay - not, crucially not, that they're using humor to deny how they feel, but that they're using humor to keep enough of the pain at bay that they can make it through the day. And it does something else, as well, letting us keep track of how the characters are progressing emotionally over the course of the film's plot (which covers at least some weeks).

So anyway, the film is not mirthless. But begad, it is powerfully bleak. The heart of the story is that Lee Chandler (Affleck), an apartment handyman in Boston, is called back home to Manchester-by-the-Sea not quite in time to be there when his brother Joe (Kyle Chandler) dies of the weak heart that's been plaguing him for a couple of years. This leaves Lee as the duly-appointed legal guardian of Joe's 16-year-old son Patrick (Lucas Hedges), whose response to all of this is to cling to whatever kind of "normal" he can get his hands on. Lee, for his part, has unspeakable personal tragedy in his life, and the very reason he left Manchester for Boston was so that he could shed ever single connecting tissue between himself and his memories, and even being in town long enough to set up funeral arrangements for Joe is causing him to have an almost physical revulsion to life and himself and damn near everybody. All he wants is to drag Lucas back to Boston, which is exactly the thing the boy least needs and wants. This is, as you might say, an impasse.

Even that prΓ©cis suggests more of a dramatic, conflict-driven movie than Manchester by the Sea provides. No, that's not right. The film set itself up to be about the conflict between Lee and Patrick; in fact, it turns out to be about the conflict inside Lee's head. The tragedy he experienced (I feel like an idiot dancing around it, but the film very much treats it like a Big Reveal, and I guess I can play along) was enough his fault that he blames himself, and not enough his fault that only some of the people in Manchester blame him, while some, like his ex-wife Randi (Williams) do not, or do not anymore. And this is the thing that Lee can stand least of all. He needs and wants to be punished, and he cannot stand the thought of being forgiven or absolved of his sins: this self-negation is at the heart of the final scene between Affleck and Williams (who is only in the film for a few minutes total, and in the process still manages to offer up one of the leading candidates for best English-language movie performance of 2016), which is a depiction of two people with far too much shared history trying to navigate their current feelings that's physically sickening - a moment of raw horror as we find ourselves completely understanding these two human beings and wanting them both to be happy and knowing damn well that there is no chance whatsoever that the scene will end without at least one of them having completely lost (spoiler alert: it ends with both of them losing). I swear, this is a totally watchable, engaging movie.

The reason it is so is because Lonergan, as a writer, is one-of-a-kind great at sussing out how people react to each other, both actively and inside their own heads (his directorial debut, You Can Count on Me, has my all-time favorite depiction of a sibling relationship in cinema), and as a director, he has an unnerving gift for helping great performers find exactly the right line readings and physical business to tell us who these people are, rather than just what they're thinking or what they want. The list of actors who've given their best performance in a Lonergan film has included, to this point, Laura Linney, Mark Ruffalo, Matthew Broderick, Anna Paquin, Jeannie Berlin, and now Affleck, whose runny-eyed, knotted-stomach portrayal of Lee is soul-bruising, in the best way. Self-destructive characters are easy; playing a self-destructive impulse as the collection of so many tiny moments of bad choices and recklessly hostile attitude is, I assume, not easy at all. And fuck, he's not even the best actor in the movie - depending on how generous we want to be to Hedges's wounded-animal physical language, and his great manipulation of his voice (he's an articulate character who, at many points, elects to be inarticulate), Affleck might only come in at third.

It is, anyway, a completely breathtaking film about humans in crisis, presented with a muted but still sharp-witted aesthetic (especially the editing, by Jennifer Lame, which is as clinically precise as Lonergan's Margaret was vividly ragged: the cutting in and around the flashback revealing Lee's dark secret, with the past jabbing into the present like a dagger, is particularly smart). Lonergan's gift for capturing the little offhand moments of life is in exquisite form: bits and pieces like Lee overhearing one of the tenants he's helping gossiping about him in the background, or a shot of a stretcher refusing to go into an ambulance, or the totally unnecessary but piercing and wise flashback to the day that Joe found out that he had a dying heart, and how his soon-to-be ex-wife Elise (Gretchen Mol) can't deal with how flippant her husband is about his impending morality. Given all that, I wish I loved it more; it is certainly the Lonergan film that's blown me away the least. Part of that might be that it really is so close to misery porn, going all-in on showing Lee's anguish and the cause for it (the flashback to his day of tragedy is shockingly brutal, maybe more than it has to be; I get that it's there to impress upon us the weight of his pain, but still), so good at wallowing in his depths that it can't quite manage to poke its head back above water when Patrick comes along to show us a more resilient way of dealing with life's hardness. Part of is that the flashbacks start to muck with the momentum. Part of it is the spectacularly awful scene where Patrick has dinner with his long-missing mother and her new husband (Broderick, going three-for-three with Lonergan), a lead-footed misstep that recalls the worst parts of Margaret without that film's "anything goes" aesthetic madness.

I mean, let me be clear: it's an excellent motion picture, so good and so unsparing that it's almost shocking that it's an awards frontrunner too. The sophistication of its portrayal of guilt and grief is a one-of-kind sort of thing, and I could watch Affleck's washed-out expressions all day long. It just feels like it could be better, maybe a little less committed to the idea that everything is pain and suffering, maybe a little shorter, maybe this, maybe that. I left less satisfied than I had planned to be. But then again, the gut-wrenching discovery that satisfaction is hard to get and sometimes entirely impossible is exactly the point of the film's faultlessly unresolved ending, so maybe the way I felt was exactly right.