At a secluded winery in Sicily, Robert McCall kills crime enforcer Lorenzo Vitale and his henchmen to obtain a key to the winery's vault and recoup money stolen in a cyber-heist. While leaving the winery, Robert is shot in the back by Vitale's adolescent grandson. Robert considers suicide due to his injury, but finds his gun out of bullets and then takes the ferry to go back to the mainland. While driving on the Amalfi Coast, Robert pulls over and slips into unconsciousness from shock, where he is found and rescued by Gio Bonucci, a local carabiniere.Bonucci brings him to a fictional remote coastal Italian town called Altamonte, where he is treated by small-town doctor Enzo Arisio. Robert gets acquainted with the locals and becomes fond of the town and its people. Robert makes an anonymous phone call to CIA officer Emma Collins to tip her off about the winery's role in the illegal drug trade disguised as normal business transactions in Sicily. Collins and other CIA operatives arrive at the winery and find millions in cash along with bags of fenethylline tablets hidden in a storeroom, confirming Robert's suspicions.Meanwhile, the members of the Camorra harass and kill villagers in an attempt to coerce them out of their housing and take over Altamonte for commercialization purposes. Robert overhears Marco Quaranta, a high-ranking Camorra member, pressurising local store owner Angelo for payments. To make an example, the Camorra firebombs Angelo's fish store as the entire town watches. Bonucci reviews video of the firebombing and calls the Italian central police for an inquiry. Along with his wife and daughter, Bonucci is later attacked by the Camorra and beaten for interfering in their operations.Sometime after, Marco demands that Bonucci set up a boat for them; overhearing them, Robert requests them to move their operations to a different location. When Marco refuses, Robert kills him and his henchmen. The Naples head of police is threatened and tortured by Vincent, Marco's brother and head of the Camorra, to find the person behind Marco's death. Vincent has Collins' car rigged with a bomb, but she survives after Robert warns her. Vincent later threatens to shoot Bonucci in front of the entire town if Robert does not reveal himself. Robert does, but before Vincent can kill him, the citizens begin to record the ordeal, causing Vincent and the rest of the Camorra to retreat with plans to retaliate the following day.Later that night, Robert infiltrates Vincent's home and stealthily kills his bodyguards. Then, Robert forces Vincent to take a lethal dose of his own drugs to kill him. Through Collins, Robert returns the money he had taken from the winery to an elderly couple's pension fund. Back in Langley, Virginia, Collins receives a promotion for her role in ending the Altamonte drug trade. She finds a note from Robert congratulating her, and declaring her mother would be proud of her - revealing Collins to be the daughter of Robert's longtime friend and colleague Susan Plummer. With the Quaranta brothers dead, Robert celebrates with the locals after their team wins a football tournament.