Taraji P. Henson, Michael Emerson, Jim Caviezel

Spoiler alert! Person of Interest's Michael Emerson enjoys playing morally ambiguous characters.

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As Lost's Ben Linus, he played a delicious cocktail of villain and hero. And even though his Person of Interest character, shady billionaire Mr. Finch, intends to make the world safer, the mystery surrounding him and his machine has us wondering: Is Finch really a good guy?

Thursday's episode (9/8c, CBS) may shed some light on the subject. When the machine kicks out the social security number of a teen who has been dead for two years, Finch is forced to question the machine's infallibility. Cue some revealing flashbacks to a younger Finch who discusses the building of the machine with a colleague (Brett Cullen, who, interestingly enough, played an Other named Goodwin on Lost.)

"We take a look at pre-injury Finch," Emerson teases. "He was a more normal guy — a more happy-go-lucky... sure-of-himself, brighter person, which is a great contrast to the kind of darker monomaniacal character that he is in the present day."

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What caused the change? Emerson says it's a combination of Finch's injury and the loss of a significant person in his life. "Along with having a damaged body, I think he got despair — he got rage," he says. But Emerson, who likes to be kept in the dark along with the audience, says he's unsure if that person makes an appearance in the flashbacks. "He has people in his life in the backstory, but he doesn't have anyone in the present story," Emerson says. "I think there is something being held back for future episodes."

But Finch does have John Reese (Jim Caviezel), a former CIA special forces operative that Finch hand-picked to be his partner in high-tech vigilantism. But the odd couple's relationship will soon fracture, thanks to Taraji P. Henson's Detective Carter, who is still tracking Reese for his late-night subway assault in the premiere episode.

"[Carter] turns out to be a very dogged and resourceful investigator," Emerson says. "She doesn't have to study Reese for very long before she figures out that he is not operating solo."

And that can't be good news, can it? "For both Finch and Reese, their lives depend on their fictional existence," Emerson says. "They cannot bear much scrutiny, or it's a danger to them and everyone else.  Elaborate shell games and ploys have to be brought to bear."

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If such measures are needed to stay out of the watchful eye of law enforcement, how then can Emerson argue that he's playing a good guy? "I don't think he is greedy or self-serving or has a lust for power, unless a lust to be an avenger for justice is a kind of power madness," Emerson says. "I think he means to do good, but obviously he is working in a way that is outside the law. His behavior is ethically and legally questionable. The borders are really blurry."

In other words, Finch, at least for now, is Ben Linus 2.0.

It seems remarkable that after his Emmy-winning turn as one of Lost's most-loved characters, Emerson wasn't immediately snatched up by another TV series. "You don't get as many offers as you might think because I think people believe that you are inundated with offers," Emerson explains. "Consequently, there is a period of a mysterious idleness. It is nice to recover a little bit and take some time off, but by the same token, you don't want to lose whatever momentum you may have or let people forget about you."

We don't see that happening any time soon.

Person of Interest airs Thursday at 9/8c on CBS. Watch a clip from Thursday's episode below: