Finch directs Reese to their newest Number and informs him that for the first time it's a Number that they've had before. Leon Tao comes flying out of a window at the address and breaks his arm, and then looks up at Reese and says hello. As two men come out, Leon explains that his newest scam involved running an online gaming gold-farming scheme. Unfortunately he ran afoul of the Russian Mafia. Reese suggests that the mobsters back off but they refuse and Reese takes them out. However, Leon is still under threat so Reese takes him to the library in protective custody. Leon realizes that Finch is the person in charge and is happy to meet him. Finch needs to go with Reese on their newest assignment and tells Leon to stay put and not touch his computers. He sets Bear to guard the forensic accountant and tells Reese that they're going to a hospital.
Finch and Reese go to the hospital and Finch poses as a contributor with Reese as his financial manager. The administrator, Sebastian Alta, shows them around and they run into Dr. Madeline Enright, the hospital's chief heart and trauma surgeon. As they talk, Finch puts a duplicate pair of Maddy's glasses onto a couch. When she realizes that she's misplaced her glasses, Finch points out the duplicate pair, which he's bugged. Maddy goes on her way and an outside security team locks down the area. Sebastian explains that they're closing down the floor for a sensitive surgery.
Maddy meets with her new patient, energy magnate Oliver Veldt, who is there to receive a coronary bypass. Veldt and his assistant, Leland Rains, insist that the operation remain a secret from the shareholders and the general public. Maddy is called to the ER to deal with a gunshot gang member. His fellow gangers have come in with him and argue about his treatment until Maddy tells them to get out of her way. Finch and Reese listen in and are impressed with her take-no-prisoners attitude.
Later, Maddy takes a break and her wife Amy comes by with coffee. As they chat, Reese watches them and Finch confirms that Amy is a charity director for a children's hospital. The two of them chat briefly and Amy says that she'll see Maddy later and leaves.
Fusco gets a call on the shooting of a man. He discovers that the man has been stripped all of identification but finds one thing on the corpse: Carter's card. Fusco calls his partner and tells her what he's discovered.
When Maddy goes back to her office, she discovers that a man is waiting for her. He introduces himself as Alistair Wesley and shows her a datapad. It has a live feed of the park where Amy is working for charity. Alistair explains that he has a sniper training a gun on Maddy's wife. To keep Amy alive, Maddy must follow a precise set of rules, which include not calling in anybody from the outside. During the surgery, she is to inject Veldt with an anticoagulant and then make a small incision in the heart. She will then let him die and Amy will be spared. Reese heads out to track down Amy and save her while Finch gets to Maddy despite Veldt's security.
When Carter gets to the crime scene, Fusco tells her that the dead man is Dusan Babic, a Croatian immigrant. Carter doesn't know who he is and Fusco shows her the card. Someone has written "6611th" on the back. Fusco suggests that his partner leave before the other cops ask questions she can't answer.
Maddy checks to make sure that Veldt is ready for the operation. She warns him that the surgery does have some element of risk but he reminds her that he's paying to make sure she doesn't make mistake. As the orderlies take Veldt to the OR, Leland continues to question Maddy's choice of procedure and she insists that it's the best possible. Alistair sends her a text message telling her to get the anticoagulant and Maddy gets the drug from the supply room.
Finch breaks into Maddy's office and hacks her computer while Reese goes to the park. He tries to spot the sniper and Finch admits that he can't run an ID check on Alistair while he's away from his computers. However, he does access the video feed of the park to Maddy's phone and sends Reese the picture so that he can triangulate and find the sniper. While he works, Finch hacks the hospital records and puts in a fake shortage of Veldt's blood type so that Maddy will have a legitimate excuse to delay the surgery without breaking Alistair's rules.
Reese pinpoints the sniper's location and moves in on him. He manages to disarm the man and shoot him in the foot with his own sniper rifle. The sniper is wearing ballistic armor, saving his life, and there's nothing on him to identify who he is. Alistair calls on the sniper's phone, well aware that Reese has intervened, and offers to buy him a drink. If Reese refuses, Alistair will have Amy killed. Reese figures that he's bluffing until Alistair has the other two snipers check in. He then gives Reese directions to a local pub and signs off.
At the station, Carter reviews Babic's background and confirms that he worked in the service industry at a lot of tech companies. One company, Fujima Technitronics, is at 66 11th Avenue and Carter realizes that someone left the number on her card to lead her there.
Reese brings Fusco in to watch Amy while he meets with Alistair. As they go in, Reese tells Finch that they're dealing with professionals and finch gets an idea. He calls Leon and tells him that they need to follow the money trail and see who had the finances to hire Alistair and his team while holding a grudge against Veldt. When Leon refuses to try and go past Bear, Finch has the accountant put him on speakerphone and tells the dog in Dutch to stand down. Leon goes to work and Finch warns him not to try and hack his computer.
Reese finds Alistair seated at the bar and draws a gun on him. He's well aware that Alistair has stationed a sentry near the door and that the man has a hidden gun trained on Reese. He tells Reese that he has several men in position to kill Amy and offers him a drink. Reese judges Alistair's accent and training and figures that he's MI-6 and his men are ex-SAS. Alistair figures Reese for ex-CIA and tells him to stay out of his way. Reese draws a gun on Alistair only to discover that the sentry has closed with him. The man tries to garrote him and by the time Reese takes him out, Alistair has made his escape.
Maddy goes to the OR and prepare the syringe with the anticoagulant. Amy sends her a good luck text message as Finch comes in and tells Maddy that he knows what is happening. He asks her to trust him, explaining that he delayed the operation by altering the hospital blood records, and promises her that they'll save Amy before she has to operate. The attending nurse, Liz Picket, comes in and tells Maddy about the delay in the blood. Maddy decides to trust Finch and introduces him as backup surgeon. Before she leaves, Maddy begs Finch to save her wife. Finch checks in with Reese, who tells him that Alistair has the park covered with his own surveillance system and that there's no way they can pick his men out of the crowd.
Maddy begins the operation but has no choice except to administer the anticoagulant. Finch sees what she's doing and tells Reese, and receives a call from Leon. The accountant tells Finch that he's hacked Veldt's records and discovered that he turned down the chance to invest in offshore wind farms. Someone has been short-selling the company's stock and if fails then the seller will make a fortune. Leon is trying to track the server that routes the stock sales and promises Finch that he'll keep digging.
Finch enters the OR and assures Maddy that everything is going fine. She calls for a break and leaves Liz to monitor Veldt's vital signs. Outside, Finch tells Maddy that Reese is trying to save Amy. Maddy steps away and takes a call from Alistair, asking why she stopped the operation. He connects Maddy to Amy to reinforce his threat, and Maddy says that she just wanted to hear Amy's voice. She assures Amy that everything's fine and says that she loves her. Meanwhile, Finch calls Reese and tells him that Alistair has someone on the inside since he knew within a minute that Maddy had halted the operation. Reese realizes that he has to move and tells Finch that he's going to get Amy out.
Carter goes to Fujima Techtronics and discovers that there's been a shooting. The security manager explains that someone broke into a clean room. As they talk, Carter sees former Agent Snow leave the building and goes after him into a nearby building.
At the park, Reese tells Fusco to create a diversion while he gets Amy out. The detective approaches a beat cop and picks a fight with him. While Amy and Alistair watch, Reese slips a cell phone into Amy's purse.
Leon calls to tell Finch that he's tracked the sale to the server and discovered Veldt's medical files. Finch realizes someone on the inside must have told Alistair about Veldt's surgery. He tells Leon to fax him everything that he's dug up on Veldt, the operation, and the stock sale.
Reese calls Amy on the cell phone and tells her that she's in danger and that he knows Amy. He tells her to stay on the phone and follow his instructions to get out of the park. Meanwhile, Finch calls Reese and tells him that Maddy is going ahead with the operation and they have two minutes until she follows Alistair's instructions and makes the incision.
Carter follows Snow into the tunnels beneath the building and finally tells him to stop. Relieved, Snow tells Carter that they're far enough underground and "she" can't hear them. The agent tells Carter to warn Snow that something big is coming and he can't stop her. Carter asks why he killed Babic to get his idea, but Snow says that he had no choice and reveals that he's wearing a bomb vest. Before he can tell Carter who "she" is, someone fires at him, hitting the lights above Snow's head. He runs off and by the time Carter gets there, Snow has disappeared.
Realizing that Leland must be the inside man, Finch sits next to him and tells him not to call Alistair. He shows Leland Veldt's medical records and figures that the assistant has been selling the stock. Leland denies everything and says that once Veldt recovers, they were going to reexamine the wind farm project. Finch realizes that Leland is telling the truth and tries to work out who did warn Alistair. He goes back to the OR as Maddy finally decides what to do. She halts the surgery and orders everyone out. Alistair, listening in, realizes that Amy has disappeared and tells his men to move in and find their target.
Liz insists on staying to help Maddy close Veldt up. The surgeon asks Finch to get her some drugs to use to keep Veldt under while she finishes up.
Alistair's men search the park and one of them spots Amy. Reese takes him down and escorts Amy out to the street. Meanwhile, Fusco leaves the park and spots a beat cop. He tells the man to offer his apology to his partner in the park, but the beat cop says that he doesn't have a partner and he's the only officer patrolling the park.
When Reese and Amy get to the street, the fake cop is waiting for them and draws a gun on them.
Veldt suddenly flatlines and Maddy realizes that someone made the incision anyway. The only suspect left is Liz, and the nurse admits that she was the backup plan if Maddy didn't go through.
Fusco arrives and calls to the fake cop. Distracted, the man turns toward the detective and Reese knocks him out.
Liz tells Maddy to let Veldt die but the surgeon refuses and goes for the equipment she needs. Liz grabs a scalpel but Finch returns and knocks her out with a light.
Reese has Fusco guard Amy while he goes back to the park. The only trace he finds of Alistair is his shattered datapad.
Maddy gives Veldt a coagulant and then starts opening Veldt's chest up. She tells Finch that he'll have to help if they want to save Veldt. He reluctantly helps her as Maddy opens up Veldt's chest and repairs the incision and then applies open heart massage. Despite his aversion to hospitals and the sight of blood, Finch manages to help and together they revive Veldt. After the surgery, Reese brings Amy to the hospital and reunites the two women.
Later, Finch and Reese blindfold Leon and drop him off on a street far away from the library. Reese tells him that Veldt survived and all of the conspirators will take a loss, and Leon is happy to hear that he helped the good guys. As he takes a taxi, Reese gets a call on the sniper's phone. It's Alistair, who congratulates Reese on winning the round of the game. When Reese dismisses his opponent as a common thief, Alistair says that they've met before in Istanbul. Reese doesn't remember him and Alistair says that he's been trained to stay out of sight. The Englishman suggests that they get a drink sometime, hangs up, and leaves for the airport.
Carter sets up a meeting with Reese and shows him the stolen security badge. She wants to know what Reese can tell her about the mystery woman and what she's up to. Carter wonders if he would tell her if he did know, and Reese congratulates her on her detective work. He admits that he can't stop her from looking, but warns her that while he has no one to lose, Carter still has her son and her life. Reese asks her how much more she wants to know.