Leon Tao is in a hotel room with his girlfriend Candi, and they kiss while Candi handcuffs Leon to the bed. Suddenly, two Nigerian scammers break in asking Leon for their money back. Candi, who had set up Leon, asks for $500 from the Nigerians before leaving. One of the Nigerians pulls out a knife and threatens to kill Leon, right before Reese busts in with Bear and they take out the Nigerians. Reese tells Leon to stay out of trouble, saying he may not be there to save him next time, just as Finch calls and informs them they have a new Number. Finch tells Reese that he's going to Atlantic City.
Reese arrives at the Venus Casino in Atlantic City while Finch briefs him on their Numerr: Lou Mitchell, an elderly watch repairman whose wife Marilyn recently died of cancer. Finch sends Reese the information he was able to gather, stating that Lou has almost no digital footprint like many his age. Reese observes that Lou likes playing baccarat, figuring he's a regular at the casino, and Finch suggests looking into Lou's finances as the man has lost a great deal of money at the casino.
The next day, Reese is at a pharmacy watching Lou, saying there's still no sign of a threat. Finch, who has hacked into Lou's bank, points out that Lou's coffers are nearly empty, and he withdrew almost all of his money following the death of his wife and has lived on social security ever since. Reese and Finch figure that Lou's gambling addiction is likely the cause of a threat against him. Reese follows Lou to a coffee shop, seeing that his fingers have been broken. While Lou chats with a waitress he knows, Finch learns that Lou was involved with the mafia, and says that the man's gambling past has come back to haunt him. Reese says he'll have Carter find out more on Lou's background.
At the NYPD precinct, Bill Szymanski shows Carter a file on Lou, pointing out his arrest record and the fact that there is still criminal activity going on in Atlantic City. As Carter takes the file and thanks Szymanski, she runs into Detective Terney, who tells her about what he learned in his disciplinary report on Detective Stills. Carter returns to her desk, where Cal Beecher shows up. He tells Carter that he's arranged a date for the two of them, and Carter asks him to help out on Lou's case while she thinks about it.
Back at the casino, Reese watches Lou redeem $1500 at the cashier's desk, and says that Lou is further into debt. Finch explains to Reese the system through which the casino tracks it's gamblers, and installs a malware into the online Blackjack game to hack into Lou's gambling information. Reese photographs a man who Finch identifies as Dario Makris, the owner of the casino. Finch sees that the police have suspected Makris of a drug operation, but have frequently dismissed the case. Makris offers Lou a chance to try out their slots, and Lou's info gets uploaded onto the gambling machine as he swipes his card. Finch is shocked to discover that Lou is consistently losing $2000 on a daily basis for the past 6 months, and Reese wonders how Lou got all that money in the first place.
At the Library, Reese figures that Lou is borrowing money to gamble himself out of debt. As Finch wonders where Lou gets the money, Reese considers the fact that Lou himself was a mobster, and Finch leaves to keep an eye on him.
Over at the police station, Szymanski is brought in by the IAB, and he tells a confused Carter that there was evidence planted against him. Carter insists to the IAB officer at Szymanski is clean, and the officer says that someone in narcotics gave them a tip about the dirty money found in Szymanski's home. An angry Szymanski says that today is the day he testifies against the Yogorov crime family.
Meanwhile at the courthouse, ADA Melinda Wright insists to the judge that the evidence was planted against Szymanski, as Szymanski was the key witness in a murder committed by Peter Yogorov, the new head of the Russian crime family. Right then, Peter Yogorov is brought into the courthouse, and Patrick Simmons shows up requesting an hour of Yogorov's time. Simmons takes Yogorov to a secluded basement, where Alonzo Quinn enters. Yogorov tells Quinn that HR is finished, but Simmons tells him he's incorrect. Quinn reveals to Yogorov that HR is responsible for the framing of Szymanski, and promises that Yogorov and his brother can make it back home in exchange for money. Yogorov agrees to the deal.
At the pharmacy, Finch watches Lou pick up a prescription. Reese, meanwhile, has beaten up a few gangsters from Atlantic City, and has learned that all of Lou's other mob associates are dead and Lou is the last man standing. Finch observes the people there and realizes that several of the other gamblers from the casino are also present at the pharmacy. Finch points out the strangeness of Lou buying a prescription two days in a row, and says that he'll have an "expert" look into Lou's finances. Reese on the other hand says he'll resume looking for answers from the gangsters.
The expert Finch has called on is Leon, who is at a spa. He tells Finch that the company that owns the pharmacy is a shell corporation, and one of their partners is Makris. Finch, who is at the coffee shop watching Lou, thanks Leon for his help. Lou shows up behind Finch and tells Finch to at least introduce himself if he's going to follow him around town. Finch introduces himself as Harold Quail of the IRS, and inquires where Lou got the money. Lou tells Finch he'll have to earn answers from him through Baccarat, one per hand. Lou gains the upper hand three times, and Finch checks his hands. Lou accuses Finch of calling him a cheater, and drops Finch's keys into a tank of lobsters before leaving.
Reese, who is watching Lou at the casino, checks in with Finch, who has returned to the Library. Finch points out that Lou is far luckier when he's not at the casino, and considers the possibility of him intentionally losing his money at the casino. Finch looks through the information on the other gamblers, and discovers that they're losing large sums of money at the same rate as Lou. Finch suggests the answer is in Makris, and realizes that Makris is in fact laundering drug money through the gamblers. He points out that the police would never suspect old people losing money at a casino. Reese sees an elderly man taking money out of a prescription container and tossing the container in the trash, and sees a large quantity of prescription containers inside the trash can. Reese figures Makris is forcing the gamblers to do this, but Finch wonders why The Machine gave them only Lou's number. As he says so, Reese watches Lou slip a few chips in his pocket, and realizes that he is skimming off the laundered money. He says Makris will be willing to kill anyone to protect his money if he finds out about what Lou is doing.
At the police station, Carter and Beecher watch Szymanski's interrogation. The IAB officer places down a picture of Anthony Marconi, but Szymanski denies any contact with Marconi besides the time his men shot him. Carter asks Cal about the tip on Szymanski's dirty money coming from narcotics, and realizes that it was Beecher who gave the tip as Cal struggles to reason with her. Cal refuses to name his CI, and says that the evidence speaks for itself. Carter asks Fusco about Cal, and Fusco says that though he knows HR isn't out, he doesn't know much about Beecher and warns that the trail leading from Szymanski's dirty money could reach a dangerous destination.
Lou is leaving the coffee shop, where Makris' bodyguards show up with guns and tell Lou he's been skimming from Makris. Reese arrives and takes down the men, and admits that he works with Finch and isn't part of the IRS. Reese tells Lou that he owes Finch some answers. In a car, Finch asks Lou why he's working with Makris. Lou says that when his wife Marilyn got cancer, he was able to use his card sharping skills at the casino to get enough money. However, Marilyn still died, and Makris eventually found Lou's name on a list of expert card sharps. Makris had come to Lou, taken his wedding ring and his wife's jewelry, and forced him to launder money for him since he couldn't get the original money back. Lou says that Makris told him the operation would only run for a few months, but he feels like Makris will force him to do it his whole life. Finch promises Lou he'll never let Makris come after him again, and gives the elderly man money and tickets to Chicago. Lou says he can't, but Finch says he knows what it's like to lose someone and that he had to move on. Lou tells Finch the story of how the mob caught him sharping and broke his fingers before throwing him out into a dumpster, and Marilyn found him and gave him something to live for. Lou gave up gambling and began fixing watches, and says that Marilyn saved him. Finch says that Marilyn would want Lou to save himself now, and Lou boards the bus to Chicago.
That night at the Library, Finch says that though Lou is safe, the other elderly gamblers are still at stake and Makris' operation is still active. He says that he doesn't have access to the information on Makris' extralegal gains, and suggests that they use "a distraction" to learn more about Makris' operation.
At the casino, Leon exits a limo dressed like a very wealthy person, and Finch briefly explains Makris' operation to him, as well as the fact that Leon is going under the alias Jason Bao, who is a playboy millionaire. Finch says that Leon's high roller dealing should attract the attention of Makris' security and give Finch enough time to hack into the casino's servers. Finch locates the casino's server room and sets up his laptop there. Reese observes the casino, and suddenly sees Lou at a nearby table. Reese sees that Lou is gambling all the money he skimmed from Makris, and says that Makris won't be happy to see Lou winning his money.
Reese takes Lou to the stairs, where Finch calls him. Lou says that he made a promise to Marilyn, and that she saved his life not so he could throw it away. He doesn't want to just run away after making a living out of laundering drug money, and doesn't want to die a loser. Finch agrees, and tells Lou he's staking him. Lou goes back to the casino table and happily resumes playing, and Reese keeps close watch on him. Makris hears more loud cheering from Lou's table and goes there. His smile abruptly fades as he sees Lou, and goes to call his head of security. Reese comes up to Makris and presses a gun to his torso, revealing to him that he took out Makris' head of security earlier. He tells Makris to let Lou play under the threat of revealing Makris' extralegal gains to the IRS and FBI.
Finch finishes collecting the casino's server data while Lou deposits $20,320,000. Makris hesitantly congratulates Lou, and the cashier makes a direct deposit. Lou and Reese leave the casino, and Reese calls Finch. He's unable to reach him, and Makris shows up behind him. He shows him a tied up Finch and Leon, who he was able to deduce as a fake. Makris has one of his guards knock out Reese.
Makris' men tie up Reese along with Finch and Leon. Makris hands Lou a revolver and forces him into a game of Russian Roulette. The gun doesn't fire on either Reese nor Leon, but as Makris forces Lou's hand to aim at Finch, Reese slams his chair and breaks free. Makris attempts to fire the gun at Reese, but no bullet comes out. Lou casually comes up near him and shows him that he cheated and removed the bullet before knocking out the casino owner.
The next day, Makris is arrested and Leon talks to Reese about his failed relationship. He goes on about how he's decided to save people, and Reese calmly asks him for a $100,000 chip that he secretly snuck away.
At the NYPD precinct, Carter shows Terney and Fusco how she was able to trace the money and learn that it belonged to a bodega run by Elias, but after an NYPD raid, the money simply disappeared and was taken by either Elias or HR. She deduces that it was a perfect way to set up Szymanski. Terney congratulates her, but Fusco warns her to watch her back. Carter gets a call from Beecher, but chooses to hang up.
That night, Finch and Lou talk at the diner. Finch deduces that Lou skimmed all the money to buy the diner, as Makris' ownership offer is off and also because Lou and Marilyn loved the place back when they were younger. Finch gives Lou the $2,000,000 watch that Logan Pierce gave Reese to repair. Lou tells Finch that his wife would be proud, but Finch looks down skeptically, leading Lou to realize that she is in fact alive. He tells Finch to go meet her, but Finch says that it's too late now.
Back at the Library, Bear happily greets Reese while Finch returns. Reese says he heard Finch and Lou's conversation, and reassures Finch he did what he had to in order to keep Grace safe. As Reese lives, Finch looks through his computer and opens a picture of him and Grace together.
Yogorov, meanwhile, is incarcerated due to Szymanski's name being cleared. He calls Simmons to tell him the deal is off. Simmons tells Yogorov he should have more faith in Quinn. Meanwhile, at a camera-free office, Quinn is talking with Szymanski and ADA Melinda Wright. Szymanski confidently tells Quinn that the Yogorovs are defeated, and that the NYPD will stop at nothing to ensure it stays that way. With a friendly chuckle, Quinn quietly pulls out a gun from a shelf and shoots Szymanski and the ADA dead. Terney comes in, now revealed to be a member of HR, and on Quinn's orders, shoots his boss in the right shoulder to cover up the crime scene.