The "Person of Interest" opening for episode "Zero Day" stood apart from the usual, representing the virus in the Machine by cutting in and out of the introductory dialog. This one small change adds to the excitement of the episode, propelling viewers into anticipation-mode.
Reese and Finch attempt to stay ahead of the numbers
With the Machine acting erratically, Reese (Jim Caviezel) is listening in on police radios for anything the Machine may be missing, while Finch (Michael Emerson) is trying to track down the source of the problem. Meanwhile, Root (Amy Acker) pulls her gun on the mysterious head of the U.S. Office of Special Counsel (Jay O. Sanders). Apparently, her work there as a fake secretary kept her up to date on everything that was going on with the Machine.
Finally, a number!
The Machine spits out the first number in 10 days, for a guy named Thornhill. But Thornhill is a weird guy. He owns an office building where people mindlessly type unrecognizable code into computers from dot-matrix printouts. Very odd indeed.
And then there are people from the shadowy company Decima -- which launched the virus in the first place -- who are trying to blow Thornhill to smithereens. But it's tough to kill someone who doesn't actually exist.
Finch finally deduces that Thornhill is the Machine. The image he has of Thornhill is a composite of three other men, and every transaction Thornhill makes is completed through the Internet. A car sent to pick him up doesn't even have a passenger. It's just a driver ordered to drive alone to Thornhill's office by himself -- with the order placed electronically.
Shaw gets involved
Finch gets a message telling him to meet at his ex-fiancee's address, but he doesn't tell Reese what's going on. Instead, Reese tracks down Shaw (Sarah Shahi) in an effort to find some help to save the Machine. Unfortunately, the cops burst in and arrest Reese while Shaw escapes, only to have her rescue him from a police holding cell with a briefcase bomb and a couple of well-hidden guns on her back. Not sure what the point is in all that, but it's cool.
Carter gets set up
Meanwhile, Carter (Taraji P. Henson) is being set up by HR. They intend to kill her, but fate intervenes. HR does not let that stop them, however. Instead, they set Carter up to look incompetent.
The Machine is a child?
Meanwhile, Finch shows up at the address and is met face-to-face by Root. If Finch helps her save the Machine, she won't kill Grace (Carrie Preston), his former fiancee. If he refuses, he loses them both. Finch agrees to help.
Root already knows that when the Machine crashes, it will reset itself at midnight with a call to a pay phone. The first person to answer wins complete control over the Machine. They will get "root access," which is exactly Root's goal. But Decima has the same plan and is guarding all the pay phones in the city.
Finch finally confesses to Root that the Machine was so advanced that it acted as a child would: It would imprint on him and attempt to protect him. Finch fixed that "problem" by basically rebooting the Machine every night at midnight and starting over. But the office with workers who entered mysterious code each day was the Machine's defense mechanism against losing its memory: They were typing in all the memory the Machine had dumped before being rebooted the previous day.
Saving the Machine
Root is horrified thinking of the Machine as a living thing that Finch "kills" each night at midnight. Root's goal is to "save" the Machine from Finch, but Finch has other plans.
When Finch and Root arrive at the library where the Machine will be calling; men from Decima are waiting by the pay phone. The two make their way up to the second level, to where Finch reroutes the call. Root plans to take that call.
Meanwhile, Reese and Shaw shoot their way in on the first level. When the clock strikes midnight and the Machine crashes, Finch quickly reroutes the call back to the first level. When the phone rings, Finch texts Reese a message saying it's for him. But Root receives a call, too. The Machine must have known what Finch was doing and made a decision about who it wanted to have full access.
So who will have root access to the Machine? The aptly named Root, or John Reese and Harold Finch? We'll soon find out when the season finale, "God Mode," airs on Thursday, 5/9 at 9 PM on CBS.
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