In Mexico in 2001, a man and a woman make love
On a subway car, a bunch of gangers enter and start harassing the passengers. Their leader, Anton O’Mara, spots a bearded homeless man and grabs his bottle. The man grabs Anton’s hand briefly with surprising strength, but then lets Anton go. When Anton and his gang close in on the man, he takes them on and quickly knocks them down, and then starts choking Anton. He studies the gang leader for a moment and then shoves him to the floor.
Later, Detective Carter checks out the assault report and talks to the bearded man. He doesn’t give her his name and asks if he’s in trouble, and she figures that he’s had special forces training. As they talk, she plays the tape and suggests that he might think he needs to be punished. Carter then takes his water glass to Forensics to have it examined for fingerprints. She confirms that he has open warrants in four different countries and been at numerous crime scenes.
A lawyer arrives and gets the homeless man, John Reese, released. Reese is escorted outside where several men inform him that their employer wants a word with him. He’s taken away before Carter can stop him. The next morning, Reese is taken to a park and meets with the man responsible for his freedom, Finch. Reese has no idea who he is, and Finch assures him that he won’t tell anyone about him. He explains that he knows all about Reese, including the work he did for the government and the doubts that he had, and that now the government believes that Reese is dead. Finch suggests that they can help each other and figures that Reese needs a purpose and a job, not psychotherapy.
Finch takes Reese to a busy street and explains that he has a way of determine when bad things will happen to a particular person. He points out a woman, Diane Hansen, and explains that she’s at the top of his list. Finch admits that he doesn’t know if Diane will be the victim or the perpetrator, but he wants Reese to follow and make sure that whatever will happen, doesn’t. Reese figures that Finch is a nutcase and starts to walk away. When Finch’s men try to stop him, Reese easily beats them up and leaves.
At home, Reese shaves and hears a newscast about how he’s wanted by the police as a “person of interest” based on the record Carter turned up. He dozes off and remembers his girlfriend, Jessica. When he wakes up, he discovers that he is in a hotel room and someone has handcuffed him to the bedframe. The phone rings and when Reese answers it, Finch tells him that he needs to learn what it means to hear someone murdered and not be able to do anything about it. A woman screams from the next room and Reese manages to break free and charge into through the door. Inside is Finch, playing a tape recorder. He tells Reese that the recording is three year’s old and that a woman was murdered in the room by her husband for the insurance. Finch notes that Reese was too late for Jessica, who was killed when he was halfway across the world. Reese grabs him but Finch says that he knows Reese left the government because they lied to him, and he promises that he never will. Reese lets him go and realizes that the recording device is government issue, but figures Finch isn’t with the government. Finch says that he isn’t and identifies himself as a concerned third party. He offers Reese the chance to be there for other people so that he can save them, and shows him a photo of Diane.
Finch takes Reese to a library closed due to budget cuts. Finch now owns the property, having bought it from the bank, and plans to use it as a base of operations. Reese notes that he hasn’t been able to find anything about Finch, and Finch says that he’s a very private person. Finch gives his new partner cover identities and funds to be replenished through a proxy corporation. On the wall is a list of Social Security numbers and Reese realizes that numbers, not names, is all that Finch has. Reese wants to know where Finch is getting the numbers, but Finch says that isn’t important and what matters is that the next number up is Diane Hansen.
The two men take to the streets and follow Diane. Finch tells Reese that she’s a successful district attorney, and Reese discusses the merits of the slow way versus the fast way. He goes with the fast way: breaking into Diane’s home and searching her belongings. Reese then steals her cell phone long enough to hack into it. He then plants a wireless camera in a neighboring building and listens in, and figures that she’s scared about something. Back at the library, Reese says that there are two likely suspects: James Wheeler, Diane’s co-counselor who she dated for a few months before breaking it off. The other suspect is Lawrence Pope, the gang leader that she’s currently prosecuting for the murder of two of his gang members and the theft of a half million in drug money.
In court, Diane examines Detective Lionel Fusco, who notes that Lawrence denied killing the two gang members. Afterward, she confronts Fusco and notes that he went off-script and never told her about the conversation, which could clear Larence. Reese, listening in, figures that something has gone wrong with Diane’s case. Finch confirms that Diane is meeting with Pope in private at his cell. She tells Lawrence that he wasn’t there and is covering for his younger brother, Michael, who was there and witnessed the murder. Lawrence tells her to stay away and that the people he’s protecting are highly placed and that they’ll kill him and his brother and Diane if she doesn’t drop it. He attacks her and Reese considers going in, but the guards pull Lawrence off of Diane. Reese warns Finch that the people responsible will go after Michael.
Jessica tells her mother that she’s meeting with a girlfriend and she’ll be back in a day. Once she hangs up, she points out that Reese will be gone for two weeks. He offers to quit to be with her and she agrees, and he tells her that he already quit rather than take the chance that she wouldn’t be there when he got back. Jessica tunes in a newscast about the 9/11 terrorist attacks.
Reese watches Diane in her office as Wheeler asks her about her conversation with Lawrence. She stonewalls Wheeler and Reese wonders if Wheeler is involved with the killers. Reese watches as Wheeler brings up Michael’s photo on his computer and figures that he’s involved after all. He goes to the school to talk to Michael, who runs away when Reese approaches him. Reese finally catches up to him and says that he needs to come with him before the killers find him. Michael calls to some nearby construction workers and claims that Reese is trying to abduct him. The boy gets away, unaware that Reese has put a cell phone tracker in his backpack. Back at the library, Reese uses Finch’s files to track down Anton.
Anton goes to a grocery shop with his gang and meets with his father. Reese comes in and the gang draws their guns on him, but he quickly subdues them, takes their guns, and leaves. Anton’s father demands to know who Reese is.
That night, Finch calls Reese and tells him that someone has picked up Michael. Reese tracks them via the GPS in his cell phone as Finch directs him to Michael. When Reese catches up to them, he puts on a ski mask and fires a gas grenade into the SUVwith Michael’s abductors. When the men get out, he kneecaps them and gets Michael out. Michael insists that they’re both dead, while Reese checks the men and confirms that they’re cops.
The next day, Reese runs surveillance on the cops, including their leader, Stills, and sees them meet with Fusco. He then meets with Finch and warns him that they’re up against crooked cops from Narcotics who are stealing from drug dealers. They kill the witnesses and then use Fusco to frame someone for the murders. When Reese says that he needs to know the source of Finch’s information, Finch explains that he was in New York City when the towers came down on 9/11. The government was given power to tap phones and e-mails, but needed someone to interpret the machine. They came to Finch, who built a machine. It saw hundreds of “irrelevant” crimes that had nothing to do with terrorism, and erased the information every night at midnight. Eventually Finch realized that the list wasn’t irrelevant, and it chewed at his conscience. The government has the drives, but the machine is still present, watching and listening. Finch has a backdoor to access the irrelevant list, but all he can access is the Social Security number. Any further information and the government would discover that Finch still has access. Reese warns that he may not be able to protect Diane and Finch admits that he never said it would be easy.
When Carter arrives at the station, she learns about the grocery store shooting with Anton and that they were taken out by one guy wearing a suit.
Finch confirms that Lawrence was stabbed and killed in his cell and that Stills and his men are covering their tracks. Reese watches as Diane receives a call asking a meeting and follows her. He steals a car and follows her to the industrial park. Stills and his men show up and approach her, and Reese prepares to shoot them. However, Diane tells Stills that Wheeler knows and that she’ll erase his files while Stills kills the Assistant D.A. Before he can do anything, Reese is captured by Fusco. They demand to know who he is but Reese refuses to answer, and Diane tells Stills to kill first Reese and then Wheeler.
The crooked cops knock Reese out and Fusco take him out to Oyster Bay to eliminate him. Reese asks him when he realized he was a bad guy and the detective says that he does it for the money. His prisoner doesn’t believe him and says that he figures Fusco is doing it out of loyalty, and he’ll let him live because he needs somebody on the inside. Reese then tosses a hidden flashbang grenade into the front. Fusco goes off the road and crashes the car, and Reese breaks out through the rear windshield. He hauls Fusco out and shoots him in the chest after confirming he’s wearing a bulletproof vest.
Reese calls Finch and tells him that Diane is the ringleader and they’re going after Wheeler. The ex-agent then hotwires a car and heads for Wheeler’s apartment.
Stills arrives outside of Wheeler’s apartment where one of his men, Azarello, is watching. The detective has Charles Robinson, one of Wheeler’s convicted felons, in the trunk and brings him in. Stills puts the gun in Robinson’s hand and tells him at gunpoint to shoot Wheeler and his son. Reese arrives and captures Azarello, and Stills freezes with Robinson when he realizes his partner is in trouble. Wheeler and his son Henry come down and Henry drops his baseball. It rolls over to Reese, who stops it and lets the boy take it.
Stills’ third man, Doyle comes out of the elevator and Reese shoots him in the leg. He tells Azarello to get Doyle to the hospital while keeping his gun on Stills. Stills says that he’ll kill Reese’s friends and family, but Reese says that he has none and he went around the world looking for bad guys just to find them at home. A few seconds later, the con runs out.
The next day in court, Diane is in court and sends a text message to Stills asking where he is. She plays a tape of the witness’ testimony, only to discover that it’s a recording of her words to Stills the previous night admitting that she’s the ringleader.
Later, the bruised Fusco gets into his car and finds Reese in the back. He warns Reese that it’s only a matter of time until someone realizes that he’s involved, but Reese says that he’s taken care of it and that everyone believes Stills is responsible. When Fusco wonders where Stills is, Reese says that he’s in the trunk, shot dead with Fusco’s gun. He tells Fusco to take Stills’ corpse to Oyster Bay and dispose of it and then leaves.
Reese meets with Finch at the park, and Finch says that he has a decision to make. There’s another number, and he warns that the numbers never stop. Finch explains that the world thinks that both of them are dead, and he does what he does because he’s also lost someone close. He offers Reese all the money he needs if he wants to leave, and admits that they could both easily end up dead for real. Reese considers his offer.
Carter brings in Azarello, who insists that the man responsible was someone in a suit. The detective tells him to tell her everything that she needs to find the mystery man... unaware that Reese is watching her. As he walks away, he looks up at a traffic camera for a minute and then walks away into the crowd.