Shortly (about four days) after the events of John Wick, former assassin John Wick tracks down his stolen 1969 Ford Mustang Mach 1 at a chop shop owned by Abram Tarasov, brother of Viggo and uncle of Iosef. John dispatches Tarasov's men in a violent fight that heavily damages his car. He then spares Tarasov under the auspices of "peace" and returns home.
After Aurelio takes John's Mustang for repairs, John is visited by Italian crime lord Santino D'Antonio. It is revealed that to complete his "impossible task" - which allowed him to retire and marry Helen - John asked D'Antonio for help. As a form of contract, D'Antonio swore John to a "Marker", an unbreakable promise symbolized by a "blood oath" medallion. D'Antonio presents the medallion to demand services from John, but John refuses, claiming that he is "retired". In retaliation, D'Antonio destroys John's house with a grenade launcher.
Winston, the owner of the Continental hotel in New York City, reminds John that if he rejects the Marker, he will be violating one of the two unbreakable rules of the underworld: no killing on Continental grounds, and Markers must be honored. John accepts his commitment and meets with D'Antonio, who tasks him with assassinating his sister Gianna D'Antonio so he can claim her seat on the High Table, a council of high-level crime lords. D'Antonio sends Ares, his personal bodyguard, to follow and keep an eye on John.
In Rome, John infiltrates Gianna's celebratory party and confronts her. Faced with certain death, Gianna chooses to commit suicide. While retreating, John is ambushed by D'Antonio's men, who intend to "tie up loose ends" by killing him. After killing most of them, John is pursued by Gianna's bodyguard Cassian. Their brutal fight is halted when they crash into the reception area of the Rome Continental. As the two reluctantly share a drink, Cassian vows revenge for Gianna's death.
After John returns to New York City, D'Antonio opens a $7 million contract for John's death, leading numerous assassins to attack him (unsuccessfully). Cassian confronts John once again in the subway. John wins the ensuing fight, but spares Cassian's life out of professional respect. Injured and desperate, John seeks help from the underground crime lord The Bowery King, whose subordinates treat his injuries and guide him to D'Antonio's location. John kills D'Antonio's men and brutally stabs Ares after an intense fight, leaving her immobilized, but D'Antonio is able to escape to the Continental. D'Antonio makes it clear that he intends to seek indefinite refuge there, and John, despite Winston's warning, shoots and kills D'Antonio.
The next day, Winston tells John that, per the High Table, the contract on John has been doubled and offered globally. Thanks to Winston's influence, instead of being executed for killing on Continental ground, John is "excommunicado" and loses all access and privileges to underworld resources. Winston delays announcing John's excommunication by one hour to give him a head start, and provides him with a Marker for future use. Before leaving, John asks Winston to send a message that he will kill anyone who comes after him. John, suspicious of everyone, flees on foot with his dog.
- Keanu Reeves as John Wick
- Common as Cassian
- Bridget Moyanahan as Helen Wick
- Ian McShane as Winston
- John Leguizamo as Aurelio
- Lance Reddick as Charon
- Thomas Sadoski as Jimmy
- Laurence Fishburne as The Bowery King
- David Patrick Kelly as Charlie
- Ruby Rose as Ares
- Riccardo Scamarcio as Santino
- Peter Stormare
- Franco Nero
- Peter Serafinowicz