Michael Emerson and Jim Caviezel

Jim Caviezel is knackered. It's about noon, and he and Person of Interest costar Michael Emerson have just concluded a gauntlet of satellite interviews at CBS' Midtown Manhattan headquarters. He apologetically struggles under our barrage of questions about what exactly has happened so far on the action-suspense drama and where it's headed. "It's a blur to me," he says. "It all makes sense when you see it. That's all I can tell you. What's in my head right now is trying to do the day's work," which over the past week or so, he says, have been 18-hour marathons. "It's a killer."

He's not the only one who's bracing for a long haul. With the series racking up impressive ratings in the competitive 9pm Thursday time slot, it looks like CBS has a hit on its hands. And no wonder. In addition to Caviezel's and Emerson's star power, POI is executive produced by suspense mastermind J.J. Abrams (Alias, Lost) and features a premise that's both tantalizingly out-there and eerily contemporary: a post-9/11 America where an all-seeing surveillance behemoth, called simply the Machine, can watch us, hear us and data-mine our backgrounds to identify threats to the state. It also spits out the social security numbers of people who, while deemed "irrelevant" for national-security purposes, are predicted to be imminently involved in criminality of some kind.

Emerson plays Finch, the gazillionaire designer of the Machine who's come to regret how his creation has ignored "irrelevants." He decides to atone for his sin by intervening in the lives of the irrelevants to prevent said crimes, recruiting Caviezel's Reese, a traumatized former black-ops supersoldier, as his partner. As a screenwriter of The Dark Knight and the 2006 feature The Prestige, POI creator Jonathan Nolan knows that with November sweeps looming, it's time to start putting some meat on the show's mythological bones and fleshing out his thus-far maddeningly mysterious leads. "I like shows that dangle the big picture forever," he says, "but we really like these characters and we're impatient to tell some of their story."

Key word: some. After about 10 minutes of grilling, Nolan finally admits: "J.J. has given us a list of things to say in  answer to these questions." Unfortunately, those answers — to questions like, Why does Finch limp? Is Harold really his first name? What is the personal loss he refers to that motivates his crusade? How did Reese's fiancée, Jessica, die? — frequently amount to "stay tuned," "possibly" and "we'll see."

Fortunately, afternoon finds the production shooting a climactic scene of tonight's episode, titled "The Fix," amid the marble-and-granite grandeur of lower Manhattan's Museum of the American Indian. There, Emerson attempts to enlighten us. "We've begun to explore backstories for Reese and Finch that would explain their psychological motivations," he says, his measured, erudite tones evoking Lost's Benjamin Linus. "We're also beginning to get a sense that there might be a little connection between some of these crimes that they're intervening in, that there might be some ongoing criminal enterprise that might occupy them for more than an episode."

More good news: This week's story line revolves around money-in-the-bank guest star Paige Turco (Damages). She's a shadowy "fixer" who moves among a variety of Gotham's criminal subcultures. As Nolan puts it, "She operates in a sort of gray zone, so she and Reese are somewhat fascinated by each other." Fascinated... and smitten? Nolan will only reveal, "She ain't going anywhere."

Emerson, meanwhile, prepares us for Taraji P. Henson's NYPD detective Carter to loom larger as the season wears on: "Our two avengers have attracted the attention of the authorities, so in addition to their vigilante work, they now have to spend more energy avoiding detection."

We also learn that November will bring an as-yet-uncast archvillain of sorts into the picture to complicate the duo's mission. Caviezel can't say how powerful or connected said nemesis will be but, as he puts it, "He's somebody's kryptonite."

Through it all, the show's centerpiece relationship will evolve and deepen, despite the pair's laconic, distrustful natures. "Over time, there are little easinesses that are creeping in," Emerson explains. "There is a kind of grudging brotherhood growing up between them, like they're two halves of one great avenging angel."

That bonding, says Caviezel, will be especially challenging for Reese. "Something's broken there," he says of his alter ego, "like a magnet that you can't put together again. But because the intention of what they're doing is selfless, they can't help at times admiring one another, liking one another."

Nolan, for his part, imagines the pair as a latter-day Mulder and Scully. "The X-Files is definitely something we had in mind," he admits, specifically the softening of the pair's odd-couple dichotomy. "In upcoming episodes you'll see that line blur a little bit. We start to see Finch take on a more active role and a little bleed from what Finch does. They kind of rub off on each other, hopefully in really fun ways."

And so far, they're holding people's interest.

Person of Interest airs Thursdays at 9/8c on CBS.

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