Bad luck and near misses are staples of every actor's story, until there's a breakthrough. Bomer's came after a run of bit parts—a little Chuck here, some Tru Calling there—when he landed White Collar in 2009.

In 2011, before he played a set of dancing (thrusting, gyrating) abs in Magic Mike—a role he'll reprise for the sequel—Bomer heard that the director Ryan Murphy, the creator of Glee and American Horror Story, was casting a film version of The Normal Heart, with a script by Kramer, and immediately lobbied for a meeting. "I wouldn't have a lot of the rights I have today if it wasn't for people like Larry," Bomer says. Marriage, for one, comes to mind. Bomer married his longtime partner, the Hollywood publicity executive Simon Halls, in 2011. The couple have three sons: 6-year-old twins and an 8-year-old. For Bomer, a role in The Normal Heart would be an act of reciprocal advocacy. "I just wanted to be involved with the project in some capacity," he says. "I didn't care what my part was."

Before speaking to Murphy, Bomer had doubts about the merits of his résumé. Murphy had no such reservations. "Matt was the first person I felt would do whatever it took to be true to the history of the part and to the millions of people who have died because of this disease," he says. "I needed somebody who was a protector of that. That meant going on a really dangerous, incredibly severe diet and going to a dark place emotionally." According to Murphy, Bomer seized on these difficult tasks, treating them as opportunities. "I've known Matt for many years," he says. "This was a Matt I had not seen before. He was relentless in his pursuit of the truth. He was incredibly hard on himself, always wanting another take. He fought for excellence. It's the first part that shows the world what Matt can truly do as a dramatic actor."

Bomer speaks about the experience with great reverence and sincerity, his typically convivial and humorous tone giving way to a serious, humble register. "It's rare that you get to play a great role that has an arc," he says. "It's rare that you get to be a part of something that, hopefully, has some significance socially or historically. And then to have a role that changes you? I think that's the best you could hope for in this profession, and that was certainly the case here. I don't think I'll ever be the same as I was when I started the job."

• • •

Halfway through our hike up Bronson Canyon's winding trail, Bomer pauses. "I'm still on the rebound," he says. It's mid-afternoon, before our hunt for tacos, and his stubble catches the sun. He comes up here a couple of times a week for the peace of it all but hasn't yet regained his stamina after his grueling role, so he suggests we sit to discuss his transformation. Resting on a gravelly bluff overlooking all of Los Angeles, the smog and buildings blending seamlessly to create a kind of ghostly beauty, Bomer draws his knees to his chest and takes his phone from his pocket. "It probably seems really narcissistic that I took these," he says, flicking through his photos. "But I thought if I did all this work, I might as well have some record of it." Before showing me the images, he takes care to lighten the moment with a joke. "This is my Wednesday selfie, y'all. Enjoy."

On the screen is a collection of discomfiting pictures, each more painful to view than the last: the sallow, sunken eyes; the concave abdomen; the bones, all too prominent. "I stopped weighing myself after losing 35 pounds," Bomer says. "I thought the number wasn't the important thing to focus on. This wasn't Biggest Loser." He consulted with doctors, participated in a 14-day alkalized-water, juice, tea, and enzyme cleanse at the We Care Spa in Desert Hot Springs, which he continued at home for another week, and sought advice from his Magic Mike costar McConaughey, based on his experience with Dallas Buyers Club. "He called me and walked me through what he did," Bomer recalls. "It was very generous, but I took a slightly different path." It took Bomer three months to attain a sufficiently skeletal figure, a period of time Murphy built into the shooting schedule. "When I first saw Matt from across the room after the hiatus," Molina says, "he was walking with a cane. I didn't recognize him. He looked like a fragile old man."

Bomer puts his phone back in his pocket and runs his finger through the dirt. "That's what I signed up for," he says. "That's my job. And it's the least I could do for Larry Kramer." Bomer also prepared exhaustively, renting out a Los Angeles theater where he'd run through lines every day, often alone. "On some level," Bomer continues, "Larry probably saved my life. He happened to be on set the day doma was overturned. In many ways, he's responsible for doma being overturned in the first place. He's an Abraham Lincoln figure—he has affected the cultural landscape of this country, and not always popularly."