NEW YORK - "The Americans" puts its audience on the spot.

Who to root for?

Do we throw our support behind Elizabeth and Philip Jennings (played by Keri Russell and Matthew Rhys), the sexy, all-American-seeming couple who in truth are Russian-born KGB spies working to bring down the United States from within?

Or do we side with Stan Beeman, their neighbor in a Washington suburb, who happens to be an FBI agent in this circa-1980s phase of the Cold War? Stan (played by Noah Emmerich) is sworn to flush out these enemies of the state, but, despite his smarts and dogged commitment, he is constantly frustrated in his mission while undermined by personal demons.

As "The Americans" returns for its second season at 10 p.m. Wednesday, the continuing obligation for its fans will be to reconcile divided loyalties and cheer for both parties, never mind that they're working in deadly opposition.

As before, viewers will likely thrill at the death-defying dedication of Elizabeth and Philip, but will identify with Stan. In Emmerich's performance, he sticks to a fine line between being a hero and being a dupe. He's a straight arrow bending under the pressures of his job, including the isolation it imposes: He has lately fallen into an affair with a beautiful Russian informant as his job keeps him from home.

Most challenging for the audience to deal with: Stan is largely unknowable. Unlike Elizabeth and Philip, whose secret lives are manifest to viewers, Stan remains a private soul to all.

"You don't know what he knows," says Emmerich. "You don't know what he's thinking."

Stan's early-on suspicion of Elizabeth and Philip seems to have relaxed into acceptance of them as the ordinary couple they pretend to be. In a future episode, he even meets Philip at a bar for a sodden heart-to-heart about his extramarital affair.

"I haven't told anybody," he tells Philip in a near-whisper. "So you can't."

Has he let down his guard beyond the point of return?

"Is he naive? Or is he (messing) with them?" poses Emmerich, who himself isn't always sure what Stan is up to. "There have been times when I interpreted things in a certain way and played it that way, then mentioned it in passing to a writer, only to find out we had different opinions of what Stan does and doesn't know."

This leaves viewers free to fret about his vulnerabilities and setbacks. So does Emmerich, whose keeps-you-guessing portrayal makes Stan one of TV's most absorbing characters.

"I worry about him a lot, I really do," says Emmerich over a bowl of lentil soup in a Greenwich Village restaurant. It's a day off from filming the series (whose New York locations prove indistinguishable doubling as Reagan-era Washington), but Stan, as usual, is on Emmerich's mind.

"Stan's so squeezed!" he says sympathetically. "Stan gets very little respite from the pain and arduousness of his job and his strained relationships. I take it really personally. The things that the character is going through, I go through as an actor. But that's what the work is, and the joy of it. It's precarious, because your internal life is being written by someone else."

Emmerich (who turns 49 on Thursday) is immersed in this, his first series, which he laughingly refers to as "The Emmerichans." But his extensive film work includes "Beautiful Girls," "Little Children," "Super 8," "Cop Land" and the landmark "The Truman Show," in which he played the turncoat chum of Jim Carrey, prompting rebukes for years past its 1998 release from moviegoers who would ask him, "How could you DO that to your friend?!"

With that film, says Emmerich, "I became known as the guy who could appear one way and actually be another way."

It's a quality that serves him well as Stan, an unassuming-looking chap, a craggy former golden boy who might have lettered in high school but now chases Communists.

"And does it in the 'analogue '80s,' " notes Emmerich. He points out how, on each table of this restaurant, a smartphone is almost as common as silverware. Not then! "Information exchange was so much more dramatic from what it is now when, if you want to find out something, you call on your cellphone or send someone a text. Back then, you had to go and find them, or drop a note under a park bench. The world lent itself better to storytelling in the analogue age than now."

Just one more reason Emmerich is pleased with "The Americans." And here's another: He lives in downtown Manhattan and tomorrow he reports for work at the show's Brooklyn studio, just across the river, minutes away.

"I asked the universe for exactly this," he says. "I decided I wanted to do a series, and I really wanted to stay in New York." He smiles gratefully. "Sometimes the universe is listening."