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Episode 221: Zero Day
Carter is called in to help with the shooting, which involved two of Elias' men and an innocent bystander killed in the crossfire. Detective Terney is working the case and Carter tells him that Fusco is busy on another assignment. He tells Carter that the Russians are responsible. Terney asks if Carter is looking into Cal's death and assures her that he's there to help if she needs anything. Carter spots Reese standing nearby and goes over to talk to him. He offers his condolences on Cal's death and Carter asks why he and Finch weren't prewarned about the murders. Reese admits that a situation has come up but they're working on it, and Carter tells him to hurry up and resolve it. She admits that no matter how bad Elias was, the Russians are even worse.
In Washington D.C, Special Counsel is on the phone, saying that they haven't received a number from the Machine in the last seven days. He informs his superior that they've confirmed that the chip in Corwin's body came from Decima, and speculates that the covert tech company is trying to destroy the Machine. As Special Counsel finishes his call, Root comes back in with a gun and demands information.
The next day, Finch is walking Bear when the Machine calls a payphone and gives him a new number. He calls Reese and tells him that their latest POI is Ernest Thornhill, the owner of a data entry company. Thornhill has apparently been buying up payphone franchises throughout New York City and Finch admits that he's been unable to hack the company's firewall.
The two go undercover at Thornhill's company. While Finch poses as an IT worker, Reese talks with Thornhill's secretary and claims that he had a business appointment. The secretary says that Thornhill is away on business and there's no record of an appointment, and Reese says he'll check back later. Meanwhile, Finch checks the sheets of data that the workers are typing in and discovers that it's pointless gibberish, all printed out on .matrix printers. As far as he can tell, the workers are simply transferring the data from one computer to another, and Reese wonders if Thornhill's company is a front.
As they talk, Root calls Finch from Special Counsel's office and asks what he did to the Machine, and why it isn't defending itself. Finch refuses to talk to discuss the matter, and Root suggests that they work together to save his creation. She mentions Thornhill and Finch wonders what she knows, and Root suggests that they exchange information.
When Reese and Finch go back to the library, they try to work out why Root is interested in Thornhill. Thornhill simply appeared out of nowhere six months ago, opened up a bank account with a deposit of one penny, and parlayed it into $20 million. Since then, he's been buying up payphone companies. Finch checks Thornhill's credit card records and discovers that he's rented a car to pick him up at JFK International that day when he returns to New York. As Reese goes to intercept Thonhill, he promises Finch that he won't let Root abduct him a second time.
Reese waits at the only road going from JFK to Thornhill's company. Finch tracks the Thornhill's GPS in his cell phone and Reese spots the rental car coming. Meanwhile, a man parks down the road from Reese and starts using his cell phone. An aerial drone closes in on Thornhill's car and Reese opens fire on the man. The drone operator drops his phone and flees, while the drone strikes and blows up Thornhill's car. Reese goes to the car and makes sure that the driver is okay, only to find the passenger seats empty.
Reese returns to the Library and Finch checks the phone the operator used. He confirms that it has a programming signature similar to that of the virus targeting the Machine, and they figure that Decima sent the man. Carter calls to tell them that the driver is in stable condition at the hospital. She's questioned some of Thornhill's workers and learned that none of them have ever actually met the Thornhill. Reese tells Finch that Thornhill must be a fake identity that someone is using. Finch disagrees and analyzes the only photo that they have of Thornhill. He discovers that it's a composite of three other photos. Finch has also checked the last email that Thornhill sent from his phone, in a public park. According to the security cameras, there's no one there. Finch recognizes the algorithm because he developed it... for the Machine. They realize that Ernest Thornhill is a fake identity created by the Machine.
Finch insists that he took precautions to make sure the Machine wasn't creative enough to do something like create a fake ID. The only reason he can think of for the Machine to create a fake identity is so that it meets the residency requirements to own a payphone. As they talk, Finch receives a text message on his computer from Root, asking for a meeting. Rather than tell Reese about it, he tells his partner to check out Thornhill's apartment. Once Reese leaves, Finch calls 911.
Once Reese gets to the apartment, Carter calls him and asks why someone rented a car but didn't use it. Reese tells her that they have it under control and advises her to look into Cal's murder. As he hangs up, Shaw comes up behind him and holds him at gunpoint. When he asks why she's there, Shaw says that she's hunting Root.
Finch meets Root in the park near Grace's apartment, and watches as his fiancee leaves for the day. Root assures him that she doesn't have any intention of hurting Grace, and explains that when the virus countdown ends, the Machine will go into debugging mode. It will call a payphone in New York City and due to Finch's programming, it will give full administrative access to the person who answers the phone. Root knows all about Decima, which engineered the virus, and doesn't want them gaining control of the Machine. When Finch hesitates, Root promises to kill Grace if he doesn't cooperate. He gives in but tells her that there won't be any killing.
Meanwhile, Simmons calls Terney at the station and tells him that Quinn wants Carter eliminated. Terney then approaches Carter and says that he has a lead on Cal's killer. She leaves with him, unaware that the Machine has been watching her through the station cameras. It tries to call Finch on a payphone. When he goes over to answer it, Root tells him that they don't have time to deal with it and takes him away.
Shaw informs Reese that Root has infiltrated The Program and gotten close to Special Counsel. As Reese starts to call Finch to warn him, the police break in and capture him. Shaw slips away before they can spot her, leaving Reese behind.
As Finch and Root walk down the street, Root figures that Finch programmed the Machine with a backdoor in case it crashed, so that the administrator would have unlimited access. Decima is trying to kill Thornhill because the CEO has been buying up payphone companies to gain control of any payphone that the Machine might use to make the call at zero hour. When she wonders how vulnerable the Machine is, Finch admits that the person who takes the call will have unlimited access for 24 hours. However, he's sure that Decima doesn't know which payphone the Machine will use for the call. As they continue walking, Root points out that Decima has men guarding every payphone in sight, meaning that the call will come to a phone in midtown. Even if Finch tells her which phone to use, they can't get to it. However, Root is confident that Thornhill has a plan so they don't need one.
While Reese awaits interrogation at the station, Shaw comes in posing as his lawyer. She plays a recording of Finch's call to 911, reporting a break-in at Thornhill's apartment, and points out that Finch wanted Reese out of the way. When Shaw asks if Reese can trace Finch, he admits that he put a tracking bug in Finch's glasses. Shaw then removes two guns taped to her back, gives one to Reese, and tosses her briefcase out into the hallway. The tear gas bomb inside explodes and they walk out, using water-soaked cloths for protection.
Root and Finch go to Thornhill's company. As she breaks in, Root realizes that the Machine created Thornhill to protect itself. When she sees the screens of code, Root realizes that the Machine has been protecting itself by downloading its own programming code and having the data entry operators enter it back in. Finch explains that when he developed the Machine, he realized that it had a personality and had imprinted on him like a child on a parent. Since he couldn't afford a Machine with human sensibilities, he designed it to erase its personality programming each day at midnight. As a defense, the Machine created a living external hard drive to backup its memory code. Root points out that even though it has survived, the Machine is all but crippled personality-wise by the constant loss and reloading of its personality programming.
Carter and Terney take two other officers to the house of Cal's suspected killer. Terney and Carter go around the back and Terney prepares to shoot her from behind. The suspect comes running out and fires at Carter, and she shoots back in self-defense, killing him. Terney reluctantly calls in backup.
Reese and Shaw follow the tracker to Thornhill's company, only to find Decima's men there. When they shoot them down, they find Greer waiting for them. He refuses to stop the virus and explains that he found it on the laptop that Reese and Kara were sent to China to retrieve. Greer informs Reese that the man who designed the virus was Finch, although he admits that he hasn't been able to locate him. More Decima mercenaries arrive and open fire, and Greer slips away in the confusion.
Greer calls his mercenaries throughout the city and tells them that the virus has revealed which payphone the call will go to: the New York City Public Library.
Finch takes Root to the public library and shows her the phone the Machine will use. Two Decima mercenaries arrive to guard it so Root goes upstairs to the building's juncture box. She tasers the mercenary guarding it and tells Harold to intercept the call from there so they can save the Machine from Decima... and from Finch's destructive programming. She plans to have the Machine tell her where she can find it and then she can go to save it.
As the police secure the crime scene, an IAB detective arrives and tells Carter that she's under arrest. Terney has already spoken with the IAB and told him that the suspect didn't have a gun. When Carter checks the crime scene, she discovers that the gun has disappeared.
Reese and Shaw follow Finch to the library and exchange shots with the Decima mercenaries. Root watches from the balcony and informs Finch that Reese has arrived. Meanwhile, Reese finishes off the last Decima henchman and checks his phone, and discovers that more mercenaries are on their way.
At midnight, the Machine reboots and goes into debugging mode. It calls and the phone near Root rings. She answers it, unaware that Finch has rerouted the call a second time and sent a text message to Reese to answer it. Meanwhile, Root tells the caller at the other end that she understands. She then tells Finch that they're going on a trip and the fun is just beginning.
Reese answers the phone and the Machine says, "can you hear me?"