Person of Interest Person of Interest

Person of Interest star Michael Emerson learned a few things about big season finales during his time on Lost.

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was unique because those cliff-hangers didn't just involve physical danger," Emerson tells "They were metaphysical too. Like, 'Oh wow, what does that mean?'"And while Emerson jokingly admits that his Person of Interest character Finch won't turn any frozen donkey wheels that make the island of Manhattan disappear, big changes are coming to the surveillance-obsessed CBS drama. "We're always looking for those tectonic moves — the big movements underneath everything," creator Jonathan Nolan says of the finale. "I think you'll see some relationships shifting again with another character on our show that people don't talk about as much: the machine."Adds Emerson: "We're so used to thinking of the machine in one way — as the ever-present source of information in the background. It's sort of omniscient but definitely under the control of its builders and operators. I don't think anyone has ever considered that the machine was capable of independent activity. I think that's a notion that comes up before we're done."

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All the while Finch and his partner Reese (Jim Caviezel) must protect their latest person of interest: Dr. Turing (guest star Amy Acker), a psychologist who caters to the rich and powerful — clients who could potentially kill to keep their secrets hidden. Worse, as the FBI closes in on Reese, he eventually finds himself cut off from Finch and Carter (Taraji P. Henson). "The circumstances lure Finch out into the world where he's more vulnerable," Emerson teases.But how vulnerable? Emerson confirms that the finale will see the return of Root, the hacker who challenged Finch earlier in the season. "In her, he has an adversary more dangerous than he ever dreamed," Emerson says. "I think he thought she was an extremely clever, almost attractive hacker. ... [But] she's going to come after him in a shocking way, a personal way. She's not going to seem nearly so charming anymore."

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But Finch isn't the only under threat. In fact, their entire operation may come undone, Emerson says. "Something unprecedented happens at the end of the finale," he says. "It's a great cliff-hanger and it will determine everything that happens for quite a few episodes when we come back in Season 2. The real physical danger will surprise the audience, and the audience will be left thinking, 'How can they go on doing what they do?' The circle must be broken, the audience will feel."Person of Interest's finale airs Thursday at 9/8c on CBS.