John Wick (Keanu Reeves) crashes an SUV into a wall. He staggers on out of the vehicle, bloody and wounded. He puts pressure on a stab wound in his gut. As he crawls to the side, he takes out his phone and watches a video of his wife Helen (Briget Moynahan) on the beach. John slumps over and shuts his eyes.Several days earlier....John wakes up on a cloudy day. He has flashbacks to him being with Helen, up until recently when she collapsed in his arms. She had an illness that eventually claimed her life. It is the day of her funeral. After the service, John's old friend Marcus (Willem Dafoe) approaches him to offer his condolences.That night, a delivery arrives for John. It's a small beagle. John finds a note from Helen. She wrote to him that she has made peace with her death, and now she wants John to find his. John weeps. He takes the dog out and looks at its collar, which has a flower on it, leading John to figure out Helen named the dog Daisy.Daisy follows John on his day as he takes his Mustang out. He stops to get gas at the same time as three Russian mobsters, including Iosef Tarasov (Alfie Allen), son of mob boss Viggo Tarasov (Michael Nyqvist). Iosef comes up to John's car and compliments it, and then asks how much he wants for it. John says it's not for sale. Iosef then goes over to Daisy, but John scares him away. One of Iosef's buddies peeks his head into the car and wishes John a good day.As John is getting into bed, Daisy needs to use the bathroom. When they get downstairs, there are two men in shadows standing before John, while a third takes a bat and whacks John in the head. He starts beating on John while Daisy whines. One of the men goes over to the dog and breaks her neck. The man pulls off his mask to reveal Iosef, who knocks John out. John later wakes up and goes over to Daisy, stroking her head.Iosef takes John's car to a shop run by Aurelio (John Leguizamo). Aurelio immediately recognizes the car and demands to know where Iosef got it. Iosef brags about who he stole the car from and that he killed this person's dog. Aurelio slugs Iosef in the face. Later, John comes by the shop and asks if Iosef came by, and Aurelio gives John his name to confirm that's who took his car and killed his dog. Even later that night, Viggo calls Aurelio to ask why he struck Iosef. Aurelio says because he stole John Wick's car and killed his dog. Viggo simply replies, "Oh."Meanwhile, John takes a sledgehammer into the basement and begins smashing the floor open. He uncovers a stash of weapons and gold coins.Viggo meets with Iosef in his home to discuss the situation. He hits his son twice in the solar plexus to reprimand him, reminding him who he just committed a crime against. Viggo tells Iosef that John Wick was associated with him once, until he met Helen and decided to leave. John apparently had a reputation as "The Boogeyman", or rather, the guy they called to kill the Boogeyman. Viggo calls John up to try and resolve the matter, but John hangs up on him.Viggo sends a team of 12 hitmen to John's home that night to kill him. John kills all of them with relative ease, fighting with the last few before stabbing the last guy through the heart. A police officer knocks on the front door. John greets him by name and asks him if there's been a noise complaint, and the cop says yes. He asks if John is back in the business, referring to the body visible behind John. John says he's just sorting some things out. The cop wishes him well and leaves.John summons a clean-up crew that he is done business with in the past to clean up the scene and dispose of the bodies. They have done business with John before and they know it won't be the last.Viggo meets with Wick's friend Marcus and asks him to kill Wick, offering a contract worth $2 million. He also instructs his assistant Avi (Dean Winters) to call for others to take the job. Marcus readily accepts.John arrives at the Continental Hotel where he stays while he conducts business. He recognizes Perkins (Adrianne Palicki). John meets another old friend, Winston (Ian McShane)- the manager and owner of the Continental. John asks and Winston tells him that Ioseph is at a club called Red Circle.John goes into the club where Iosef and his buddies are. As soon as they spot John, he begins shooting at them while Iosef runs away. John kills every hitman in his path, but he loses Iosef as he flees in a getaway car.At night, Marcus gets to the roof of the building across the street and sets his sights on John in his bed. From the mirror, he sees someone entering. He fires a shot to warn John. It's Perkins. She starts shooting at John while he dodges her. She tells him that Viggo has doubled the contract to $4 million if she breaks the rules of the hotel and kills him. He fights Perkins with difficulty until he gets her in a headlock and offers her mercy for information. She tells John that Viggo keeps most of his assets (cash and blackmail evidence) in the basement of a church. John knocks Perkins out and leaves her with Harry (Clarke Peters), a business acquaintance.Harry keeps Perkins cuffed to a chair, unaware that she has dislocated her thumb to slip out. She gets out and puts a pillow over Harry's face before shooting him.John goes to the church where Viggo keeps his secret stash of money. After shooting the other guards in the church, John forces the priest to guide him to where the money is. He lights it all on fire.Viggo learns of the fire moments before he is caught in a hail of gunfire courtesy of John. Although he kills most of Viggo's men, he is knocked out when an SUV rams into another, knocking John to the ground. Viggo captures him and wonders why he's gone to such great lengths for revenge over a car and a dog.John tells him that the dog was a gift from his dying wife, and that Iosef took that from him. Viggo leaves him with his henchmen for them to suffocate him with a plastic bag. However, Marcus is watching from the next building, and he shoots one hitman in the head to let John take out the other. John gets his gun and shoots at Viggo's getaway car, leaving only him alive. Viggo is forced to tell John that Iosef is hiding in a safe house in Brooklyn.The safe house is guarded by armed men, but none of that stops John from killing them and storming the place. Iosef once again tries to make a run for it, but John catches him and finishes him off.In retaliation for Iosef's death, Viggo has his goons find Marcus at his home. There, they beat him until Viggo and Perkins shoot him to death. Viggo calls John to tell him this, just before leaving for a helicopter to get out of the city.While waiting for John to come to Marcus's home, Perkins is called to a meeting with Winston, the owner of the Continental Hotel. She is met Winston and four men. Winston tells her she's broken the rules of the Continental and her membership has been terminated. The four men execute her.John finds Marcus's body and sets off to take down Viggo. He finds the villains heading to the chopper and tries ramming into them with his car. Viggo makes Avi go out and kill John, only for John to ram into him with his car. Viggo tries to push John's car over the edge, but John gets out safely. The two then fight hand-to-hand in the rain. Viggo tries to stab John, but John pushes the blade into himself (to gain leverage to break Viggo's arm) before grabbing the knife (from his stomach) and sticking it in Viggo's neck. He leaves him to die.We go back to the first scene where John is still bleeding. After watching the video with Helen, he is inspired to keep on going. He goes into a dog shelter and tends to his stab wound. He then takes a pit bull puppy with him, and they go home together.