It's always the quiet ones, isn't it? Person of Interest continued its full-speed hurtle towards the end with a whopper of an episode in "The Day the World Went Away," which represented the two biggest character changes not just for the season, but for the entire series. It also happened to be the milestone 100th episode for the techno-thriller, which celebrated the only way it knows how: by ripping our hearts out with a painful death and paralyzing us in fear over what's to come and how it relates to our real world. Ahhh, good old Person of Interest.

We're almost at the point in the series' run where the numbers of the week need to give way to the overall war between super A.I.s, so if these last four episodes are going to stick to the show's formula, it'd better make these numbers count. And yep, I'd say making Harold Finch (Michael Emerson) the number of the week was a fantastic way to do that. To be fair to Finch, it was his own damned fault that the Machine spit his number out of a pay phone. Because he retraced his steps to happier days when he was on a first date with Grace, and because Samaritan had nothing better to do, the evil computer box was monitoring significant places in Team Machine's life and Finch's cover was blown. The calm and satisfied image of Finch reminiscing about happier days would be a stark contrast to the nuclear bomb that was dropped later; we just didn't know it yet. How could we know it?

Long story short, Team Machine dropped what they were doing and did all they could to protect Finch from Samaritan's agents, who showed up in full pursuit, well-armed with a secret super computer that can move ones and zeroes around and buy anything it can dream up. You can't just drive a highly armored SUV with a .50 cal machine gun off the lot of your local dealer.

"The Day the World Went Away" featured a pair of the series' best action sequences: one with Shaw (Sarah Shahi) and Root (Amy Acker) bantering about their relationship status and the metaphysical world and how we're all just shapes and simulations while unloading an armory's worth of lead into oncoming Samaritan agents, and another with Root and Finch in a luxury sedan being tailed by said .50 cal-equipped SUV, before Root drove the car with her foot, popped out of the sunroof, and unloaded on the SUV with a big-ass gun. My dear Root is the stuff of dreams.

Which is what made what happened next so painful. Root has always known her place in the pecking order of their mission. It's the Machine first, then Finch, then everyone else, including her. So when she glimpsed a sniper trying to take Finch out, she swerved the car and took the bullet herself and... grab some tissues... later died at the hospital. (Couldn't she have swerved the other way?) It's actually the second time in the episode Finch witnessed a friend getting shot trying to save Finch's life; Elias (Enrico Colantoni) took a slug right in the forehead a few scenes before, but his death may get lost in the ether while we all mourn over the loss of Root. (We'll get to more Root in a bit.)

Person of Interest: Is Finch finally ready to let the Machine run free?

Throughout the series, Finch has been built on two things: his morals in relationship to the responsibility of being the father of the Machine and the precautions needed to ensure it doesn't spin out of control, and, admirably, the safety of his friends. The two ideas came into direct opposition with each other, and as Finch was held by the police for his involvement with Root's shooting and his mysterious background, Finch made an epic decision: He was finally ready to let the Machine fight back. He did not want to see any more of his friends killed in this war.

In a speech that would give Michael Emerson all the Emmys in a just world, a cornered Finch admitted that he's run out of options. Though he's being interrogated by a detective, Finch didn't even know the cop was there and instead turned his focus toward Samaritan, promising to kill it, but was still deciding how many of his own rules he's willing to bend to accomplish it. Emerson was as powerful as anyone on television at this moment, seething with rage and just barely staying in control while he expertly finessed this massive character moment for the man he's played for five years. It was equal parts mesmerizing and terrifying to see Finch come to this point, but you couldn't help but pump your fist when he opted to release the hounds.

We've always thought that Finch kept the Machine on a leash because he was worried about it falling into the wrong hands, but what we didn't realize was that Finch was worried that his hands were the wrong ones. Whoa! But, pushed to the brink and aching over the deaths of Elias and Root (the latter of which he didn't even know about), Finch felt he had no choice but to give power to his computerized child with the goal of taking down Samaritan at all costs and ending this war once and for all.

Person of Interest producers haven't ruled out a reboot

We got a glimpse of what the Machine could do, and it turned the series from techno-thriller to techno-horror as the Machine cut power to the facility Finch was being held at and unlocked all the cells holding prisoners while chaos reigned and Finch presumably made his escape. It is SO ON, Samaritan.

But back to Root. The only thing keeping me from going to a table store and turning over every table I see in anger over Root's death was the symbolic rebirth of Root at the end of the episode that was simply perfect. Root's relationship with the Machine has always been one of the show's most fascinating ones. In a sense, she was the physical manifestation of the Machine. She was in direct communication with her, she spoke for her, and she championed her as not only a deity but also a solution to the world's ills. Earlier in the episode, Finch agreed to let the Machine choose its own voice in order to directly communicate with Team Machine (just the first hint that Finch was ready to give the Machine more power), and in the final moments, Finch answered a pay phone as he was being sent into holding at the police precinct, and on the other end of the line was Root's voice. The Machine chose Root's voice because Root always spoke for the Machine and because it was a way to keep Root alive. It's never easy to lose a character near and dear to the audience, but we all knew the war wouldn't end without a fatality, and Person of Interest managed to find a clever way to keep that character around. In a sense, Root is closer to the Machine than she ever was when she was alive, and I like to think that would make her pretty happy even if we're sobbing hysterically.

As for Shaw and Finch, yikes. They're not going to be happy, and I'd hate to be in Samaritan's virtual shoes right now. Three episodes left to go, folks, and I don't think Person of Interest has ever been better. This episode was an instant classic.