John Wick (Keanu Reeves) was born Jardani Jovonovich in Belarus. He was an orphan who was taken in by the Ruska Roma crime syndicate, where he was raised as an assassin, eventually rising to become the top enforcer of the Russian Mafia and known as Baba Yaga (the one you sent to kill [the] Boogeyman) under crime boss Viggo Tarasov (Michael Nyqvist), who deemed him so ruthless that many came to respect and fear him. At the beginning of the first film, Wick has been retired from being a hitman for five years after undertaking an impossible task for Tarasov, wiping out all other organized crime syndicates in New York City in order to be allowed to leave to marry Helen (Bridget Moynahan) before her eventual death from cancer, leaving him known as a legend in the assassin underworld worldwide.

Every assassin in the world sticks to a strict code for conducting business, revolving around the Continental hotel chain, which serves as neutral ground for the underworld, where all business is strictly forbidden on all its properties,with each manager—including Winston Scott (Ian McShane), Sofia Al-Azwar (Halle Berry), Julius (Franco Nero), and Shimazu Koji (Hiroyuki Sanada)—swearing their fealty to the High Table, a council of twelve high-level leaders of world society, while paying for services within the underworld with specialized gold coins,[8] used as both fiscal and ethical currency to acquire goods and services,[9] as well as honor-bound favors—a specific variety of which, a marker, binds one's soul to an unbreakable blood oath between two individuals, in exchange for a specific task undertaken by each party for the other, for which one serves as the bearer until one day on-which they intend to claim the favor owed.[10] Every assassin is bound to follow two rules, or risk being made excommunicado if broken — 1. No business is to be conducted on Continental grounds. 2. Every marker must be honored.