Somewhere in a frigid mountain range, a bald man arrives by helicopter to a secret training facility owned by the ICA; the International Contract Agency. He is then greeted by, Diana Penelope Burnwood, one of the agency's handlers. Diana escorts him down a hallway to his quarters and prepares him for his training. She asks a few questions to him, concerning his professionalism in taking the lives of other people. He considers taking lives as "random" and "disordered". Later, the man is interviewed in a interrogation room by Diana and training director and former assassin Erich Soders. Soders expresses doubt about him and his origins, asking Diana to watch her new trainee closely.
The newcomer is put through assassination training, where he must eliminate an actor playing infamous thief Kalvin "The Sparrow" Ritter in a simulated setting, and another where he is required to complete the same "mission" again, but to improvise and learn on the fly. The man aces both exercises, to and moves onto his final test - re-enacting Soder's 1979 assassination of chess player turned Soviet spy Jasper Knight. Soders, fearing that the man will become a better assassin than him, rigs the final test against him so he'll fail. Despite this, the man manages to pass his final assessment, leaving a defeated Soders to begrudgingly approve him for duty at the ICA. As the two leave the mountain facility, Diana asks the man for his name, to which he tells Diana that he simply doesn't have one, merely a number designation; "47". Diana, at 47's request, makes it his name; Agent 47, and they start their business together.
That was two decades ago.
Years pass, and 47 proves to be a master at his craft, clearing a slew of contracts and assassinating many people around the world. A mystery man narrates over these kills, and notes that 47 is the best of the best when it comes to assassination, nobody coming close to his record or skill. He mentions that they also live in that world too, and questions the world that 47 has helped create.
47 is tasked by Diana to head to Paris to infiltrate an auction held by IAGO, a global spy ring. 47 is tasked with killing IAGO's heads - fashion mogul Viktor Novikov, and his partner, spymaster and former supermodel Dalia Margolis, before they can sell a list of MI6's undercover agents. 47 completes his mission, unaware that the day before, that same mystery man from earlier had claimed all of Viktor's files, and marked him for death by leaking them, leading to MI6 to issue the contract to the ICA. Shortly after the mission to Paris, 47 gets another contract from a shareholder of biotech company Ether. He is tasked to wipe out Silvio Caruso and Francesca De Santis, two scientists from the company who are engineering a weaponized virus that would disrupt the ICA's business, and to destroy the virus prototype, which 47 does with ease.
A week passes, and an agent from Ether, Hajun, contacts his bosses regarding his investigation into the assassinations. He is ambushed by the mystery man, who reveals he was targeting his organization by subtly using others to do it for him. Hajun hands over a key hidden in his tie, while warning to the mystery man that "If you have a weakness, Providence will find it", but he scoffs at the threat before shooting Hajun.
47 later heads to Marrakesh, where civil unrest is brewing after fraudulent banker Claus Hugo Strandberg is broken out en route to prison. Building contractor Hamilton-Lowe wants 47 to dispose of Strandberg, who is held up at the Swedish Consulate and cannot leave due to a riot outside, and Moroccan army general Reza Zaydan, who intends to commit a Military Coup via a False Flag Operation. After 47 completes his mission, someone sneaks into a vault in New York and steals every Providence operative's files. One of the agents sent to investigate concludes that Providence is being attacked by an assailant in the shadows, and sets to work fixing this problem. In the meantime, 47 heads to Bangkok, Thailand to kill singer Jordan Cross and lawyer Ken Morgan. Cross, who killed his girlfriend Hannah Highmoore a year ago, managed to evade justice thanks to his father, media mogul Thomas Cross, who hired Morgan to defend him by any means necessary. However, this contract was not simply placed by the Highmoore family as revenge for Hannah's death. In actuality, it was a gambit by the mysterious man to draw Thomas out of seclusion, kidnap him at Jordan's funeral, drain him of his money, and then execute him.
In an airport lounge, Diana and 47 overhear the news of Thomas Cross' murder. The two realize the act couldn't possibly be a coincidence and discuss the possibility of a third party secretly hiring them to kill people while getting all the benefits from a series of contracts made by someone else, naming that third party a "Shadow Client". The ICA soon gets a lead on who the Shadow Client could be by tracking the information to hacktivist Olivia Hall, sniffing out her trail to a farm in Colorado being used as a training ground for a militia under the Shadow Client's wing. This secretive militia is led by environmental terrorist Sean Rose, who was seen when Thomas was kidnapped. At the behest of Erich Soders, 47 is forced to kill him along with three other prominent leaders of the militia - ex-Mossad interrogator Ezra Berg, former anti-terror analyst Penelope Graves, and former assassin Maya Pavarti. After killing all four targets, 47 and Diana realise that Sean Rose was not the Shadow Client, and 47 stumbles across a room proving this, seeing multiple people that he already eliminated; all of his hits were connected to Providence, a collective group of people secretly controlling the world's affairs from the shadows. Diana and 47 also learn that someone has been tracking 47, with hits of Alistair Beldingford and Alvaro D'alvade, among others, being pinned on a map of 47's hits. Finally, they learn that Erich Soders is part of Providence as well. Realizing that the ICA has now been compromised, Diana tells 47 to escape the farm. Outside, the Shadow Client tracks 47 with a sniper rifle, while relating his past with 47 to Olivia Hall, mentioning that he knows 47 "better than anyone".
Days later, the ICA's Board of Directors approve Soders for elimination. 47 heads to the luxurious GAMA hospital in Hokkaido to eliminate Soders, who is undergoing a heart transplant in exchange for selling information about the ICA's operatives to Providence. 47 also eliminates Yuki Yamazaki, a Providence lawyer overseeing his defection.
Much later, Diana is on a train when a member of Providence also goes to her table, commenting about the Shadow Client attacking them while manipulating the ICA into doing so. He gives her an offer, in which ICA will help his organization find and eliminate the Client, claiming Providence is less evil than the Shadow Client, whom he calls a terrorist. Diana initially refuses, but the member offers her information about 47's past, leaving her to reconsider refusing his deal...
