Kenneth Lonergan knows quite a lot about marinas in Massachusetts.

“There’s a big one in Gloucester, and there’s a small one also in Gloucester, there’s one in Rockport. There’s a really teeny one in Manchester,” he says.

Lonergan had some difficulty in deciding which would appear in Manchester by the Sea , the writer-director’s simple, staggering look at grief. Simplicity may be the film’s best quality, an achievement all the more notable in how difficult that is to achieve. If our conversation offers any hint to how he pulled it off, it’s in this moment, in which the filmmaker rattles off detail after detail about the location in which the film is set (and was filmed). He knows it as intimately as any non-local possibly could, and there’s warmth and affection in his voice for both the place and the people. These details — mileage, hockey rinks, a wealth of marinas — are the things that helped bring his story to life, and the effusive way in which he describes these details hints at both fondness and gratitude..

“There’s two big competing boat repair businesses in Manchester, side by side. They don’t speak to each other,” he continues. “There’s just so much there, so you literally just point the camera and you’re going to see something interesting.”

Listening to him wax more or less rhapsodic, you’d never guess that Manchester ever belonged to anyone but Lonergan. This wasn’t an idea that came to him out of the blue, but rather one that was handed to him by another artist. When we ask him about how he felt about the concept when Matt Damon approached him, he speaks up immediately: “[It was] Matt Damon and John Krasinski, actually.”

This won’t be the first time Lonergan makes a point of giving credit where it’s due. As with his feelings about the region in which the film is set, each time a new collaborator’s name comes up, he doesn’t hesitate to tip his hat, outline the reasons for someone’s brilliance, and generally spread the love. With credit properly assigned, he goes on about how he felt about the seed that became his critically lauded film.

“I don’t remember, frankly. I liked the idea. I thought it was very compelling. I liked the idea of trying to write something truthful about someone who’s dealing with a severe tragedy and still trying to function, about the people around him trying to help him … of everyone trying to take care of each other in the midst of this unspeakable thing that happens.”

Unspeakable is an apt description of the tragedy that irrevocably changes the life of Lee ( Casey Affleck ), Manchester ’s protagonist. We first meet Lee shoveling snow and serving as the super for several small apartment buildings in Quincy. His seems a small, empty life, marked by the occasional spat with a tenant and a bar-fight or two. That all changes with the death of his brother, Joe ( Kyle Chandler ), whose will designates that custody of his son, Patrick ( Lucas Hedges ), should go to Lee. Surrounded by memories and confronted with the responsibility of caring for someone else, Lee finds it harder and harder to escape the horrors of his past and the people he left behind, including his ex-wife, Randi ( Michelle Williams ) — and as he’s enveloped in his loss, so is the audience.

When the time comes, the film doesn’t shy away from the source of Lee’s incredible distress, and though the brutal truth isn’t uncovered in full until the film’s back half, Manchester is far from coy. This is no tawdry reveal. Lonergan plays a clever and more affecting game, allowing the story and its central figure to simultaneously block out the horrors that live in the past and remain utterly unable to escape them. As such, Lee’s memories intrude on the present with increasing frequency and difficulty as he travels home, a choice that’s as much about the business of telling a story as the business of creating a character. It’s impossible to imagine the film without it, but as Lonergan tells us, months and months of struggle preceded that small discovery.

“I just couldn’t find a structure that was working for the material; it didn’t seem satisfying or interesting,” he tells us. “Then I came [to the idea] of using a flashback or memory structure, and that opened the door for me to be able to write the script … I honestly just threw out everything I had that I didn’t like, and that landed me at the beginning of what’s now the film, with him shoveling snow outside of one of the apartments he works at. Then, having written a lot of the material from the past, it was there to be put in as a series of memories that overcome him as he’s driving home.”

Throughout our conversation, the importance of the film’s sense of place comes up again and again. All that driving matters to the film. It’s quietly but undeniably inextricable, making the story one that, as Lonergan makes perfectly clear, could only exist on film — and this from a Pulitzer Prize-nominated playwright.

“I don’t think it would work as well [on stage]. I wouldn’t like to see the story without them having to drive along the highway with the snowy trees going by, or certainly without them being able to go on the boat and see the marinas, see the environment. Hearing about a boat is one thing, being on a boat is something else.”

With that, we’re back to Massachusetts. It’s clear that Lonergan wanted to make sure the world of the film felt lived-in and did the work accordingly. He learned how far each town was from the next, the demographics, where people live and work, and, of course, where there were marinas. It wasn’t just to lend the story the air of authenticity, though it certainly does that. Lonergan believed these fine details would inform Lee’s journey in simple but meaningful ways — and he was right.

“These details affect important things,” he says. “The Manchester hockey team, they don’t practice in Manchester, they practice in Gloucester, and the Gloucester team is part of the Rockport team … Lee wants to get [to hockey practice] in time to be the first to tell Patrick that his father’s passed away, so he has to leave the hospital at a certain time. So that puts some pressure on the hospital, and it puts pressure on his drive. Not a lot of fun making these trips where you have to live with this kind of news, you know.”

That snowy drive does quite a lot to set the tone of Manchester by the Sea. As Lonergan points out, it’s the first instance in which Lee’s memory flashes back. As the wintry landscape glides past and Lee moves closer and closer to the home that holds so much heartbreak, the sense of cold becomes almost palpable. The frost echoes throughout the film — in Lee’s reserved demeanor, in the comforting energy offered like a cozy blanket by his friends and family, and by the icy reception he receives from strangers who know only the story that defines him and not the man himself.

The similarity may be inescapable, but it wasn’t intentional: “It was just a happy accident,” Lonergan explains.

“I tried very hard to stick to the prosaic [and] practical, on-the-ground level. I let the metaphorical side take care of itself, if there even is one … The winter was very important to the story, because the story requires the final burial of the father to be delayed, so there’s a certain amount of difficulty. Lee wants to remove his nephew from the town and get out of there as quickly as possible, and the fact that it’s the dead of winter and the middle of the school year makes that even more awkward than it might otherwise be. Then, slowly, over time, he does warm up to his nephew, and I didn’t mean for it to be a parallel for the seasons changing, but the parallel is there. The closer he gets to someone, the more danger he’s in. It’s a genuinely impossible problem.”

Lonergan’s understanding of and compassion for Lee becomes clearer and clearer — though the screenplay, an Oscar front-runner, makes that abundantly clear all on its own. There’s one person whose knowledge of the character’s emotional life may rival the writer’s, and that’s Casey Affleck, an actor about whom Lonergan speaks with genuine admiration and affection. “He really worked so hard on this part, so thoroughly, he really wanted to know everything about the part and the circumstances. We talked a lot about what [Lee is] like, why he behaves the way he does, why he says the things he says, why he declines to say the things he declines to say.”

Lonergan’s praise of the actor is unprompted and casual. “It’s really a pleasure to work with someone who’s that interested in exploring things at such a practical and emotional level. He’s also in his real life an extremely decent and responsible person, a very supportive person. That, I think, finds its way into the character all over the place. [Lee’s] a guy who’s trying so hard to be there for his family, even though it’s agony for him.”

Lonergan’s praise for Affleck isn’t limited to his diligence, nor his personal and professional conduct. “He’s a brilliant actor,” he states simply. “His emotional life is so full and his sense of humor so profound.”

It’s difficult to imagine Manchester without Affleck, in no small part thanks to the humor Lonergan praises. For a story so dark, so marked by tragedy, Manchester is a remarkably funny film. Much of that humor comes courtesy of Lee’s interactions with his nephew, Patrick, meaning that two of the people most directly weighed down by grief are also the sources of much of its levity. We ask Lonergan about how he approached the balance of darkness with humor, and as with metaphor, the writer seems to view things as being much simpler than they may seem.

“I find them to be pretty much one and the same thing,” he tells us. “For me, there’s no real separation between the two … You look at the work of someone like Almodovar, and he not only blends tragedy with comedy; he blends tragedy with absurdist comedy in some cases. It just seems to me to be very seamless … One informs the other. One is part of the other.”

Viewed through that lens, Manchester by the Sea becomes, if anything, more human. The laughs aren’t there because a writer knew his film needed a way to occasionally tiptoe out of the darkness. They’re there because that’s simply what happens to us. A man and his nephew argue about how far away a certain city may be. A boy panics when frozen food falls on him. When asked what exactly he does with his two girlfriends, the same young man responds in short, “strictly basement business.”

In Lonergan’s words: “This happens in life all the time. They’re driving back from the hospital, and they get to the garage door. He says, ‘There’s a bleeper. I don’t have the bleeper.’ It’s just funny. There’s this very slight obstacle, the word ‘bleeper’ sounds funny in a North Shore accent, and finally it’s funny for a second … Life is a bit of a tapestry, and many, many of the threads in it are quite amusing.

“That’s what’s so great about working with actors,” he adds, with something like amazement in his voice. “They come up with all these things all the time.”

He may be in the midst of a career triumph, but even now, Kenneth Lonergan still focuses on the simple things — and one of them is giving credit where it’s due. Manchester by the Sea may be a group effort, and yes, it’s filled with tremendous performances, but such an effort — if you’ll forgive the boat metaphor — needs a strong, compassionate hand at the helm.

If that hand belongs to a man who knows the ins and outs of every marina on the Massachusetts shore, so much the better.