In Kenneth Lonergan’s new film, Manchester by the Sea, there’s one moment that’s so powerful, it’s almost unwatchable. Lee (Casey Affleck), who fled his New England hometown in the wake of a family tragedy but has returned to care for his orphaned nephew, runs into his estranged wife Randi (Michelle Williams) on the street. The former lovers had once built a life together and suffered great loss, yet with the passage of time they had become strangers. Over lunch at a vegan restaurant in West Hollywood, Affleck says the hard part of shooting the scene wasn’t letting the emotion out but reining it in. “The challenge,” he says, “was to have all of those feelings and hold it without weeping and wailing and gnashing your teeth. To be there, and not be there.”
Affleck, 41, approaches a lot of his work with this blend of sensitivity and critical detachment. He politely deflects personal recognition for his work. To hear him describe it, the credit goes to writer-director Lonergan: “He creates characters that you believe in.” Of his co-star Williams, he says, “She is so good that you have to throw out all your plans and just be there with her.” Yet despite this self-effacement, Manchester is unmistakably Affleck’s film. The actor, who has delivered consistently strong work across many genres over the past two decades, carries the movie on the strength of a textured performance as a grieving father who unexpectedly has to step back into a parental role.
To do that, Affleck says, he had to give himself over entirely to the heartbreaking material. During production, Williams recalls, her co-star was deeply absorbed. “The Casey that I know and spend time with now seems pretty carefree and loose, easy and happy–that’s not the person I knew then,” she says. “He was really seized by the material and the character.”
In conversation, Affleck is genial but introspective. “Some people go, ‘I was so moved, and I don’t really know why,'” he says. “When I read the script, I was crushed every time I got to a certain point. It pulls out your emotions for you.”
The current moment of political discord–half the country is elated, the other half despondent–might seem like an inopportune time to release an emotionally shattering family drama. (Audiences are often more inclined to seek out a lighthearted escape during such times.) But for all of Manchester‘s weight, it’s also a compelling look at the complex interior life of a type that’s often pigeonholed but rarely examined.
In Lee, Affleck finds a taciturn handyman from blue collar roots who’s disinclined to emote. But as his reticence gives way to begrudging tenderness, it becomes clear that Lee isn’t cold–he’s just afraid to love given the fragility of life. Those are the types of difficult characters that Affleck says he loves best. “Parts where the character could easily be two-dimensional, I want to flesh them out and make them real humans,” he says. “I look for roles in which that’s hard to do.”
Although he found it in Manchester, he admits that he was still surprised by how hard it hit when he saw the film. “I had read it and worked on it and shot it, but still, the emotions crept up on me,” he says. “Suddenly I was so moved.” Affleck knows it’s a tough film to watch, but that makes it all the more worthwhile–even the really painful scenes. “My favorite movies still make me cry,” he says, “at all the same places.”
This appears in the November 28, 2016 issue of TIME.