End of Watch is the apotheosis of Gyllenhaal's quest—102 minutes of blood-soaked, adrenaline-producing drama propelled by the bond between his Officer Taylor and Taylor's partner, played by Michael C. Pena. The effortlessness of Gyllenhaal's acting has been obvious since Donnie Darko, but nothing is easy about Officer Taylor—or the film.

"I'd envisioned his cop as a locked-down, even-keel guy," says End of Watch's director, David Ayer, who grew up around those cops in South Central. "And as the director, I'm supposed to be the one with the world map. Actors just see the road they're on. But as the shooting progressed, there were so many unexpected things he was giving—it's unbelievable." Gyllenhaal attributes some of that experimentation to the extreme preparation necessary for the film. "Five months, for a 22-day shoot," he recalls. "Three nights a week in ride-alongs with cops. Fight training every morning at a Kenbo Karate dojo, and I got the shit kicked out of me. Then the shooting range, shooting past each other's heads, with live ammo. There's a simulated fire in the movie, but Dave wanted us to feel what that's like, so he had us do a controlled burn."

"What's that?"

"That's a Saturday where me and Michael Pena drive down to Orange County, dress like firemen head-to-toe, and suddenly we're there just sitting in the middle of a burning building."

Cast and crew understood the commitment required for the film, no one more than Gyllenhaal. "Dave told me right off that this was going to affect my soul," he says. "'Friends are going to say, That's the Jake I've always known, but somewhere deep inside, you'll know otherwise.'"

The waiter who brings our fried-chicken main event has served Gyllenhaal before. A good-looking and extremely fit kid, he's apparently had trouble linking the bearded nerd before him to the sex symbol the waitstaff is buzzing about downstairs. He says he's seen one of Gyllenhaal's films. "No, I recognize you. I get it now," he says, but he still seems dubious. "And I still really don't know who you are, either," Gyllenhaal says, smiling. "But it's nice to see you again."

The conversation bleeds into Gyllenhaal's on-set friendships that have endured: At his 31st-birthday party, half the guests were friends of 20 years, the other half LAPD officers he'd recently met. According to Ayer, they were the ones Gyllenhaal talked to all night. "I realized these are some of the best actors I've worked with," Gyllenhaal says. "I do a scene a day, maybe. They do 15 scenes every day—their word for it, crime scene—with much higher stakes."

His mien raises the question of where Gyllenhaal draws the line now: between the personal and the professional, between risk-taking and recklessness, between a challenging next project and a fanciful one.

"Every journey starts with fear," he says. "And I could say that's what I want to embrace now. A real experience. Connection with the people I'm working with, so I'm helping them make something. And I want, overall, to trust what I know is right. There have been many times when I haven't. If that's what you asked, it's what I'm asking myself now: Where is the line? What is the line? There's so much context, it can be almost impossible to find. It comes down to finding the beating heart of a story—what's this really about?—then remaining true to instinct in telling that story." He looks straight at me—no, through me. "And I just had a déjà vu," he says, tearing into his fried chicken.

I mention the physiological link between déjà vu and the exhaustion Gyllenhaal must be feeling, the brain's ability to process—

"No, this had happened," he corrects me, then his volume drops precipitously, "and now it's happened again."

That "moment relived" was at the heart of Gyllenhaal's attraction to Source Code and its eight recurring minutes. It's a microcosm of his life in front of the camera, with take after take offering chances to finally get it right. Gyllenhaal is a storyteller who just happens to work as an actor. He was a child of the industry but not a typical child actor. His father, the director Stephen Gyllenhaal, and his mother, the screenwriter-producer-director Naomi Foner, wanted a normal childhood for him. He first appeared on the big screen at 11 as Billy Crystal's son in City Slickers but couldn't take parts that interfered with his schooling (L.A.'s Harvard-Westlake and then Columbia, where he studied Buddhism and English literature) or his after-school jobs (as a lifeguard and a busboy, sometimes both). Hollywood trappings abounded—Paul Newman taught him to drive a race car, and a young Steven Soderbergh rented the family's garage apartment—but they mostly added up to what he calls "fluency in the filmmaking language."