Grief is a terrible animal, red of claw and tooth, and once it gets hold of you, there is no way of knowing what it will do to you. Over the last year, I've watched a dear friend of mine struggle with back to back losses of two of the most important people in her life, and at times, I've genuinely worried that it would be too much for her to take. This is a strong, vibrant person, and grief landed on her in a way that very nearly crushed all of that joy and vitality right out of her. I've had my own bouts with profound sorrow over the last year as a result of the end of my marriage, and while I feel like I've reached the other side of all of that, I remain shaken by just how damaged I was by things. For the first time in my adult life, I had to turn to a professional for help, and it turned out to be exactly what I needed.

One thing I've learned for sure is that no one can judge anyone else's sorrow from the outside, and we are not all built to bounce back when life kicks us in the teeth.

Kenneth Lonergan's Manchester By The Sea is an extraordinarily wise and well-observed film about what can happen to someone when life gives them more than they can handle, and Casey Affleck's lead performance is, simply put, the model of what great film acting should look like. What makes this such an unusual film, especially here at Sundance, is that it not only avoids easy answers, it posits that there are no easy answers in life. So many of the movies that play here set up a situation where one or more characters is struggling with grief, and someone comes into their life to heal them. Sometimes it's with humor. Sometimes it's with love. Often there's a road trip or a task of some sort that has to be completed. And by the end of the film, sure enough, that grief has been wiped away.

Bullshit, says Lonergan. It's not that easy. In Manchester By The Sea, when we first meet Lee Chandler (Affleck), he's working as a janitor in Boston, taking care of several buildings, and Lonergan takes his time setting things up. There is a good deal of gentle character humor in the film, but never in a way that undercuts the reality of what's happening. Lee is obviously troubled in some way, but it's more a matter of being so internal, so withdrawn, that he's almost invisible. The few emotions he's able to share tend towards anger, but even that seems like something he has to work hard to drag to the surface. For the most part, he's just there. Numb.

Then he gets a phone call. His brother Joe (Kyle Chandler) has died, something the family has been worried about for several years since he was diagnosed with congenital heart failure. The rest of Lee's family is still based in Manchester, and he has to leave work and drive home to help deal with the arrangements. He thinks it should take a week at the most, until he attends the reading of the will and learns that Joe has named Lee as the guardian for Patrick (Lucas Hedges), Joe's 16-year-old son.

One of the things that Lonergan does so well in the film is play with memory, making it feel the way memory really feels. I know that for me, memory is something fluid, something alive, something that I do not consciously access. Instead, it is something that washes over me at unexpected times, triggered by connections that may not even be clear to me. It happens all the time, and I assume it's true for most people. I'll see something, and it might not even be the main focus of the scene, and it'll trigger a sensory memory so strong, so complete, and then just as quickly, it'll be gone. And they're not always memories I want. Kyle Kinane does a brilliant bit about the way we have no real control over memory. Memory has power, too, precisely because of that. I think it would be nice to be able to control what you do or don't retrieve from the memory banks, but Lonergan knows that memory is cruel and that it can be like a physical assault at times, taking a toll.

Jennifer Lame is building an impressive body of work as an editor, and when you look at films like Mistress America or Frances Ha or Price Check, it's clear that she has a real voice in her collaborations with directors like Noah Baumbach or Jake Schreier. There are cuts in this film meant to represent jumps back and forth in memory and in time that are like physical blows. Lonergan's writing is sophisticated here, and so is the razor-sharp rhythm of the cutting. They're both so emotionally precise, so powerful, so smart, and it pays off when Lonergan lands the biggest emotional punches in the film. There is a way of doing this that would be very sentimental, designed to tug at the heartstrings. This is more emotionally mature than that, and absolutely the result of the collaboration, with Lesley Barber's score a perfect complement, never leading, always emotionally powerful by being spare. Lonergan's not looking to pummel you here. He's not driving you towards the big Hollywood epiphany.

Performance after performance after performance, Manchester By The Sea is filled with such impressive work that it helps create that seamless world for Lonergan. The community is part of the story here. Whatever it is that broke Lee Chandler happened in Manchester, and from the moment he shows up at the hospital, he's uncomfortable, ready to cut and run. And wherever he goes, people seem to know something about him, something about his past. It's awful, but it's not heavy-handed. It's just present wherever he's present. It's something he carries around with himself. And much of the film is about how people react to him, react to this black cloud that sort of follows him, as well as his relationship to Patrick, both past and present. Lucas Hedges does terrific work in the film, and his is arguably the most important relationship to Lee in the film. For this young actor to really push Affleck in their scenes together is impressive, because this is Affleck at his very best. He's bringing his fastball, so to speak, and so is everyone else in the film. I loved Gretchen Mol's work in the film, and there's a fantastic role for Matthew Broderick. Both Kara Hayward and Anna Baryshnikov give knowing, empathetic performances as Patrick's high school girlfriends. Those parts could be nothing, but Lonergan really wants to paint a picture of what normal is for this kid when this life-shattering thing happens to him. Heather Burns is really wonderful in a brief but revealing role, a clear bellwether of just how damaged Lee really is.

Special mention has to be made of Michelle Williams and Kyle Chandler, though. Thanks to Lonergan's approach to memory, Joe is very much a part of this film, and we see how Chandler and Affleck were as brothers. It's beautiful stuff. They have terrific chemistry, and that's also true with Williams, who plays Lee's ex-wife. She was part of whatever it was that destroyed Lee, and her attempts to reach out to him here, to communicate with him, are the best individual scenes I've seen here this year. She's amazing, and so is he, and Lonergan wrote these amazing scenes for them and both actors know they've got this gold and daaaaaamn, they're good.

At 135 minutes, the film feels to me like it gives everyone room to breathe, to be real people. He uses every minute of the film. It's nuanced and it's alive and it's the exact sort of thing you come to a festival to see. This is one of the films of 2016 that will be essential for every film fan. It feels like the most complete and effective film yet for Lonergan, which should be good news to fans of the underappreciated Margaret and his debut You Can Count On Me. This is the work of a mature film artist, someone who has really found a comfort in the way he can use film language to punch a giant emotional hole in an audience. This film looks easy, but that's part of the marvel that is the screenplay. It's beautifully structured, and human, and it says something new about a subject that seems mined out. I was knocked out by it, and I've been thinking about scenes and lines from it ever since.

Manchester By The Sea will be in theaters later this year.

A respected critic and commentator for fifteen years, Drew McWeeny helped create the online film community as "Moriarty" at Ain't It Cool News, and now proudly leads two budding Film Nerds in their ongoing movie education.