War is coming on Tuesday's Person of Interest.

In the midseason finale, the Machine used Root (Amy Acker) as an avatar to have a one-on-one chat with fellow artificial super intelligence Samaritan. When those talks devolved, Samaritan decided to show the Machine just how quickly it could create global chaos by setting its sights on the U.S. stock exchange.

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In the exclusive sneak peek below, Root maps out for Finch (Michael Emerson) just how serious this threat is — the collapse of the financial system could create revolts, starvation... and war." Our cold war just turned hot," Root says.

Fortunately, the Machine has created a failsafe for Samaritan's attacks. Unfortunately, it has to be deployed on-site at the stock exchange and Team Machine is down a person with Shaw (Sarah Shahi) in the wind.

What will the team do? Click play below to find out and then keep reading to get Acker's take on being the Machine's avatar, just how ugly this "hot war" is going to get, and the one thing that could break Root's faith in the Machine.

We've seen Root relish her relationship with the Machine, but do you think she was shocked to serve as the Machine's avatar in the meeting with Samaritan?
Amy Acker: I feel like there was a sense of a hesitation or maybe a fear. There was a sense of she's decided, "The machine told me, this is what we're going to do," but maybe that she didn't think that was what [the Machine] would have done. While she still feels maybe honored to be the avatar for the Machine or to be able to speak on behalf of her, she wasn't quite sure what good was going to come out of this meeting.

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How hard was it to shoot that scene? Are we to believe that Root is dictating exactly what the Machine wants her to say, or is she interjecting her own thoughts?

Acker: It was a hard scene. I mean, I have passed on messages from the Machine in previous episodes... but it wasn't a dialogue. Those were the same questions I was asking. For the most part, the words that are being spoken are the exact words that the machine has given her to say. That's Root's doing her best to present the face that the Machine wants to present to Samaritan without giving any of her opinions away. But maybe there are certain points where she can't help but be taken aback by what's happening or what's being said.

The end of the least episode, Samaritan seems poised to attack the stock exchange. Are all bets off in the next episode?

Acker: Yeah, there's a major thing that's happening: These gods are going to war. Samaritan said, "I'm going to destroy you," and the Machine has almost admitted defeat and then yet has said that we're still going to fight you to the end. The fight is now about to begin. It's a really exciting, interesting episode. It was kind of the climax of what's happened in this season. Everyone is in danger and there's a lot to be worried about, and I think this episode is really going to determine what happens for the rest of the season.

But Shaw is also in the wind. How does Root decide where to focus her energy?

Samaritan knows what Shaw looks like and is out to kill all of them, and Shaw will be the first on the list. Root's heart is telling her, "I've got to find Shaw and we've got to protect Shaw." And at the same time, if we don't stop Samaritan now and we don't find a way to win this war, it doesn't matter. Everyone's going to be dead.

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We know Root truly believes in the Machine, but is there any part of her that might, in the interest of self-preservation, bow out of this seemingly unwinnable fight? Acker: I feel like it will be hard for her to abandon the team completely because the Machine's speaking through her and is a part of her. So, even if the Machine knows she's going to lose, her agents are not going to surrender. But based on how this season has led up, the Machine has been silent and Root has felt sort of lost and abandoned without hearing the voice and without talking to her. So, it's been a struggle for Root, and now she's having to question and wonder what the plan is. This all-powerful being that's she worshiped up until this point now seems to be able to be defeated by this other thing.

If she's questioning the Machine a bit now, would you she follow it blindly? If the Machine told her to leave Root behind for the greater good of the fight, could she do that? Acker: I think that would be a really bad situation. If Root was required to hurt one of the team herself or if she knew that one of them were going to be killed because of actions that the Machine was doing, it would be a real struggle for her. And I think that I don't think she allows herself to believe that the Machine would sacrifice any of them. She sees the machine as this benevolent being that is only out to kill the bad guys. Root doesn't let into her mind that there would be a scenario where the machine would want to kill one of her friends in order to make something else go right. So, if that happened, I'm not sure what her relationship with the Machine would be after that point.

Person of Interest airs Tuesdays at 10/9c on CBS.