Charlestown, a blue-collar neighborhood of Boston, Massachusetts, has the highest rate of bank robberies in the world. During the heist of Cambridge Merchant Bank, four heavily armed men disguised in skeleton masks with dreadlocks and black hoodies quickly seize control and hold assistant manager, Claire Keesey, at gunpoint while she nervously fumbles opening the safe. Although the assailants timed their raid to coincide with the expiration of the bank’s security time lock, one robber grabs her shaking hand and calmly tells her to take her time while another grows agitated and pushes her superior to the ground. Once the safe is opened and ransacked, the thieves’ plans are momentarily thwarted by a man outside knocking to get in. When he leaves, they prepare to depart by dousing the surroundings with bleach, but the volatile robber becomes further aggravated upon realizing an alarm was triggered during the disruption and pummels the manager’s face with the butt of his AK-47 rifle. As his partner tries to restrain him, the perpetrator’s hoodie is knocked over, secretly revealing a “Fighting Irish” tattoo on the back of his neck to Claire. Impulsively, the aggressive robber takes Claire hostage, and she is bound and blindfolded in the getaway van while his partner reassures her that she will not be hurt. She is released on a beach and walks, barefooted and blind folded, toward the water. Arriving at the scene, FBI Special Agent Adam Frawley is briefed by Boston police investigator, Dino Ciampa. Bleach prevented the acquisition of DNA evidence and the getaway van was torched, leaving him with no forensic leads to begin his investigation. At the same time, bank robbery mastermind, Doug MacRay, meets up with his collaborators James “Jem” Coughlin, Albert “Gloansy” Magloan and Desmond “Dez” Elden at Charlestown’s inoperative Boys & Girls Club Ice Skating Rink. Jem announces that Claire’s driver’s license shows she is a neighbor and vows to stalk her. In her interview with Frawley, however, Claire refrains from mentioning the tattoo and defensively asks if she needs a lawyer. Frawley tells her people with lawyers usually end up guilty and he thinks she’s fine, but notices her shaking hands and reassures her it is normal to have residual effects. Back at the ice rink, Doug snatches Claire’s driver’s license from Jem, declaring him too impetuous for the job and taking on the surveillance, himself. That evening, Doug and Jem deliver cash to Fergus “Fergie” Colm at his shop, Town Flowers. At a bar, Jem tells Gloansy and Dez about Doug’s father, Stephen MacRay, who accepted extended jail time instead of ratting out his cohorts. As Doug orders a non-alcoholic drink, he encounters Jem’s sister, Krista Coughlin, who was his girlfriend before sobriety. She pretends to drop drugs in his juice, and when she asks if he misses partying, he admits that he does. Back at his apartment, they make love, but when he denies her appeal for him to say he loves it, she leaves in haste. Unable to sleep, Doug goes to a Narcotics Anonymous meeting. Doug keeps surveillance on Claire and follows her into Monument Laundromat, where she asks him for change. He denies her request, but then comforts her as she cries seeing bloodstains on the shirt she wore during the robbery, and he asks her to have a drink. Meanwhile, Frawley blackmails a local drug dealer for information on the robbery. Learning the thieves circumvented the alarm by breaking into the security “junction box,” he spearheads his investigation with a subpoena of Vericom company logs. When Claire and Doug meet, she tells him about the robbery, and although Doug apologizes, she tells him it’s not his fault and that Frawley reassured her side effects were normal. Doug presses her about her involvement with the FBI, but she informs him that they don’t have any leads and admits to omitting her knowledge of the “Fighting Irish” tattoo for fear of having to testify. Frawley’s case breaks with information about Dez, who is a Viacom employee with days off that coincide with other recent bank robberies. As Claire works in the Charlestown Community Garden and inquires about Doug’s parents, he evasively says his father is in the suburbs and his mother left when he was six years old. Despite his attempts to find his mother, she was never seen again and he presumes she is in Florida with his grandmother. Frawley presents photographs of the four thieves to a team of agents and describes their histories, including Jem’s nine years in prison for manslaughter and Doug’s failed prospect of becoming a professional hockey player. At a café, Claire tells Doug that sunny afternoons are depressing because they remind her of the day her brother died, and when Jem makes a surprise appearance, he narrowly misses revealing his tattoo to Claire. Back at their shared apartment, Doug and Jem argue about Doug’s relationship with Claire. Jem pressures Doug to get the next heist underway despite his reservations, pointing out that he waited nine years in Walpole prison for him. Doug visits his father in jail to discuss his intention of leaving Charlestown and asks why he never looked for his mother. Stephen relates that she was no different from the drug-addicted girls with unwanted pregnancies currently in the neighborhood and not worth finding. Later, at Claire’s apartment, she admits seeing Doug’s photograph on the “Local Heroes” board at the Boys & Girls Club where she volunteers as a kick-ball coach in the dry hockey rink. Doug regrets throwing away the opportunity to be a pro-hockey player, then resituates to Claire’s bedroom because his uncle, who lives across the street, has a view into her living room, and they consummate their relationship. As Doug predicted, the next heist is riddled with impediments. After breaking away from an armored car guard who captures one of the robbers at gunpoint, the team, disguised in nun costumes, is chased by the police through the narrow streets of Boston. Several gun battles ensue and, despite Frawley’s orders to close the Charlestown Bridge, they ultimately escape because one cop turns away. Frustrated by a lack of DNA evidence, Frawley demands his crew to procure a fingerprint so that he can bring the men in for questioning. Police cars race to Doug’s workplace at the Boston Sand & Gravel Co., where he is handcuffed without a fight. At police headquarters, Frawley tells Doug he will make sure he dies in prison, but Doug refuses to be intimidated and insinuates that the fingerprint they reportedly collected from the scene is bogus. Upon Doug’s release, Frawley orders phone and computer surveillance. Back at Claire’s apartment, Doug inquires why she quit her job at the bank, presents her with a diamond necklace and suggests that they go away together so he can change his life. They make a pact, despite Doug’s warning that there are things about him that she doesn’t know and won’t like. Later, when Dino presents Frawley with a taped phone conversation between Doug and Claire, he goes to her apartment and, noticing her diamond necklace, reveals Doug as a suspect and says she needs a lawyer after all. At the cemetery where Jem committed murder years earlier, he tells Doug that the florist has a new job for them, but Doug says that he is done and planning to leave Charlestown. Jem accuses Doug of abandoning Krista, her illegitimate daughter and their community, and a fight breaks out when Doug insists that he is not responsible. Jem points out that he killed only to defend Doug and demands appreciation through Doug’s sustained involvement. Doug is grateful for their brotherhood but stays resolute in his decision to leave, telling Jem that if he wants to shoot him, it will have to be in the back. He proceeds to the flower shop to announce his resignation. As Fergie strips thorns off long stemmed roses, he threatens to castrate Doug if he quits, saying he did the same to Stephen by getting his mother hooked on the drugs that prompted her to commit suicide. Fergie warns that Claire will be killed if Doug does not acquiesce. Shaken, Doug arrives at Claire’s apartment to find her traumatized by the news of his involvement with the robbery. Despite his pleas, she kicks him out and begs to never see him again. Upon finding a funeral wreath for Claire back at his apartment, Doug returns to the florist and agrees to do the job, but vows to kill Fergie and his partner, Rusty, if anything happens to Claire. The following day, Doug finds Claire at the Community Garden, and promises never to hurt or lie to her again. Later, Fergie briefs the robbers on their most ambitious assignment to date, clearing out the cash room at Fenway Park. Still in hot pursuit, Frawley questions Krista at a bar about her work for Fergie, dealing the drug Oxy to launder stolen cash, and calculatingly asks if Doug ever bought her a diamond necklace. Krista, high on drugs, finds Doug in an apartment across the street from Fenway on the day of the heist and begs him to take her away with him. Spiraling into a jealous rage, Krista mentions the necklace, and Doug forcefully pushes her to leave. She crashes in front of a school and Frawley uses the opportunity to blackmail her for information about Doug in exchange for the custody of her daughter. Disguised as Boston police officers, Doug and Jem are led through the inner corridors of Fenway by a man indebted to Fergie. As Dez disconnects security cameras, Doug and Jem take control of the guards, force their way into the cash room by threatening the families of the men working inside, and push immense stacks of cash into duffel bags. As they make their exit in the ambulance dock, Doug notices the street outside is lined with policemen in riot gear and federal agents. A gun battle ensues inside, and Gloansy is shot in his bulletproof vest. Grenades are launched into the dock, briefly deafening the robbers and as Dez stands, disoriented, he is shot through the head by a sniper. Gloansy suggests that Doug and Jem get back into their police uniforms and escape while he acts as a decoy by driving the ambulance through the gates. He is shot and killed as the ambulance smashes into an FBI Mobile Command Unit. While Feds and police officers face off for control, Doug and Jem part ways and blend into a crowd of uniformed men. Security from within Fenway reports the heist was orchestrated by policemen, and Frawley redirects his search for Doug and Jem among the scattering cops. Carrying the duffel bag of cash across his back, Jem is conspicuous and upon orders to stop, turns and fires repeatedly at Frawley. After a short chase and gun fight in a public intersection, Jem is shot dead as Doug looks on and drives away in a squad car. He heads to the florist for retribution, killing Rusty and Fergie and taking their stockpile of cash, but news of the incident reaches Frawley who deducts Doug’s new location and moves his stakeout to Claire’s apartment. With a view into Claire’s window from his uncle’s apartment, Doug again apologizes over the phone and, despite seeing Frawley listening in, says he wants to see her. She tells him to come, but then furtively signals a warning by comparing her feelings about the encounter to a sunny day. Doug escapes the scene dressed in his uncle’s bus driver uniform, leaving a hostile note on Frawley’s car and burying Fergie’s cash in the Community Garden for Claire. A plaque reading “An Anonymous Gift in the Memory of Doris MacCray” lines the newly restored Boys & Girls Club Ice Skating Rink where Claire watches children play, and, far away, Doug stands on the porch of a remote hut looking across the water that surrounds it. As stated in the note he left her, he says that he must pay for his actions but he knows he will see her again.