"This isn't hot," Colin Farrell says, standing in the damp inferno of a sauna at a Russian bathhouse in West Hollywood.

"It gets worse, but you'll get used to it," the 36-year-old Dublin native promises, his familiar brogue brightly reassuring in the sweltering haze. I'm sprawled on a bench, liquefying. My hair is close to combusting, my brain steadily confit-ing in its own juices. Farrell is upright, unmoved—a seasoned veteran of saunas and a believer who preaches the restorative powers of a good schvitz.

"When I got out of rehab, I went to New York and randomly moved into an apartment two doors from the Russian & Turkish Baths," he says. This was 2006, following his turn as the pouty, slickly pomaded reincarnation of Crockett to Jamie Foxx's Tubbs in Michael Mann's big-screen version of Miami Vice. He'd made an epic run of it—the near-instant success, the standard Hollywood Rich-and-Famous Contract with its all-access allotment of money, celebrity, sex, drink, and drugs in potentially fatal doses. At age 29, he found himself fat-faced and exhausted, ill from good fortune and bad choices.

"For a one-man band who didn't have, like, three or four other dudes helping trash shit and talk smack, I did fairly well," he says, with a certain degree of gentle forgiveness for his past self—and no interest in going back.

"The bottom line is I ended up miserable. I'd done enough of a job of flagrantly abandoning myself in a very loud and public way that I began to fall apart, you know?"

Anyone who needs a refresher in this spin on the be-careful-what-you-wish-for Hollywood cautionary tale can dial it up online anytime: the drunken expletive-laced tirades, the interview wherein he compares the convenience of call girls to pizza delivery, the sex tape that, despite all legal efforts, didn't stay private.

So he checked himself in for treatment, chucked the bad-boy brand, and entered a new period that still, seven years later, feels to him like uncharted territory.

"I'm not Scandinavian," he says, returning to the subject of the baths. "I had no background with saunas. But a friend said, 'Check 'em out,' and I did. And that was it. From then on, I was there three or four hours a day for four months."

We've been in the heat maybe 10 minutes, but they're long, slippery minutes that make it hard to grab hold of an idea like four hours. Time feels different when you're trying not to think about it, and maybe therein lies the allure of the sauna: a slow-paced, cleansing, away-from-the-world zone in which the afflicted life-aholic can rest and reset.

"There was a time when I needed to do three or four films at once," Farrell says. "It was the best place for me to hide." He's less frenetic now, taking fewer gigs but giving each more of his attention, more of his self. He's just wrapped Saving Mr. Banks, with Emma Thompson. Next month he's headed to New York to begin shooting Akiva Goldsman's adaptation of Mark Helprin's supernatural novel Winter's Tale, with Russell Crowe and Will Smith. In between, Farrell practices yoga regularly, reads compulsively, and takes road trips—solo. "I'm shit print compared to what I was before," he jokes.

Time regained is the reward of rehab, and it was, for Farrell, an unfamiliar commodity.

"Honestly," he says, "I've got eight hours a day now that I didn't have before, when I was drinking every day for 18 years."

What to do with that windfall? How to process the reclaimed clarity of those found hours? These are questions never far from Farrell's mind.