Paul Kersey (Bruce Willis), who lives with his wife Lucy (Elisabeth Shue) and college-bound daughter Jordan (Camila Morrone), works as a trauma surgeon at a Chicago hospital. During the Kerseys' lunch, Paul's brother, Frank (Vincent D'Onofrio), asks him to lend some money to pay off a debt, to which Paul reluctantly agrees. As the Kerseys leave, Frank gives the valet, Miguel (Luis Oliva), the keys to their car and joyfully tells him that Paul has "got the money". Miguel goes to pick the car up, but also take pictures of Paul's address from their car. On the night the Kerseys are to have a birthday dinner, three masked men invade the Kerseys' home while Paul is at work. Both Jordan and Lucy are shot; Paul is informed at the hospital that Lucy died, and Jordan fell into a coma. Police Detective Kevin Raines (Dean Norris) is one of the officers tasked with the investigation.Outraged that the police are unable to solve the crime, Paul becomes a vigilante stalking the city streets to deliver his own brand of justice and to find the men who ambushed his family. When a gang member is brought in to the hospital after getting shot, Paul steals his weapon after it falls off the table. He proceeds to prevent a carjacking, a video of which goes viral; Paul is dubbed Chicago's "Grim Reaper". Later, Paul finds his watch on Miguel's wrist when the latter is hospitalized. Paul orders one of the doctors to fibrillate Miguel's heart three times, killing him. Paul discovers a photograph on Miguel's phone with his address. The phone receives a text, telling him to meet at a bar in the suburbs. At the bar, Paul talks to the owner, Ponytail, and says that he was sent by Miguel. A suspicious Ponytail secretly messages Fish (Jack Kesy), his partner in crime.Ponytail reaches for his gun, but Paul stabs his hand with a dart and forces him to return the goods he stole from Paul's house. Fish arrives and accidentally shoots Ponytail. After shooting Fish in the leg during a shootout, Paul steps on his wound for information. Fish then divulges that Lucy's shooter is Joe (Ronnie Gene Blevins), a car mechanic who works in an auto body shop. He kicks Paul in the groin and gains the upper hand but is accidentally killed by a falling bowling ball. At the auto body shop, Paul ambushes Joe while he is working under a car. He tortures Joe for information by cutting his sciatic nerve with a scalpel and pouring brake fluid into the wound. Joe divulges that their leader, Knox (Beau Knapp), shot Lucy. Paul then removes the jack lifting the car up, causing it to crush Joe's head.The hospital informs Paul that Jordan has regained consciousness. At the hospital, Paul tells Jordan what happened to Lucy. After he rejects a phone call from an unknown contact, a message warns Paul that the police will be informed about his actions unless he answers the next call. The contact, Knox, orders Paul to meet him in a bathroom at a nightclub. Paul calls Knox's phone number to see it ringing in a stall. He shoots the stall, only to find that it was a ruse. Knox confirms the gunshot to be Paul's, and the two engage in a shootout, which ends when Knox escapes. When Paul returns home, Frank discovers Paul's gun collection and confronts him, but Paul insists on continuing to protect the city.Knox and two other thugs prepare to invade Paul's home; Paul hides Jordan in a closet under the stairs. After killing the two thugs in the upstairs bedroom, Paul heads into the basement, where he suspects Knox is located. There, Knox emerges from the darkness and shoots Paul in the shoulder. Before Knox can kill him, Jordan yells out her father's name. Knox taunts Paul and states the house will go up in flames, as he approaches Jordan's location, Paul retrieves an assault rifle from a compartment under a table and as Knox arrogantly turns around, Paul shoots Knox dead. The police then arrive; Detective Raines suspects that Paul was the "Grim Reaper" but decides to cover up that Knox attacked the house, thinking that Jordan might identify him.Later, Paul drops Jordan off at the university. A radio program playing in the background hopes that, wherever the "Grim Reaper" is, he stays out of society. As Paul is leaving, he spots a man who steals a bag from a bellhop. Paul points at the thief with a finger gun.