A group of individuals bound by a chilling addiction—the urge to kill—holds regular meetings for mutual support and understanding. Their hidden community plunges into chaos when an assassination attempt is made on Senator Kyle, portrayed by Sam Hazeldine, in the heart of the city.
Guiding this group is The Man, played by Gary Oldman. One day, he travels to London and crosses paths with Jade, brought to life by Jessica Alba. Jade is slated to carry out the hit on the senator while he's in London. However, things take a dramatic turn when an old acquaintance, now a bouncer at a bar, recognizes her and forces her to leave, prompting The Man to demand her immediate departure from London.
The very same day, Jade encounters a seemingly random female prostitute, who turns out to be an assassin. In a tragic twist, the assassin shoots and seriously injures Jade.
As the group's clandestine meetings progress, they start to suspect that powerful forces are manipulating their gatherings. This fresh suspicion arises when Alice, played by Rhyon Nicole Brown, joins the circle and meets Joanna, portrayed by MyAnna Buring. Among the noteworthy members are Leandro (Michael Socha), Ben (Elliot James Langridge), and Calvin (Tim McInnerny). As tensions mount during discussions about the senator, Alice becomes increasingly uncomfortable and attempts to exit the meeting, only to be stopped by Krystal, played by Elizabeth Morris, who also had a hand in Jade's earlier attack. Finally, Markus, portrayed by Tommy Flanagan, enters, marking his presence among this eclectic group.
Known as Killers Anonymous (KA), this self-help organization is meant for those who once lived a life of murder and wish to leave it behind. During an intense session, Joanna hears strange noises from the ducts, hinting at a hidden observer, who is later revealed to be Molly, a girl played by Isabelle Allen.
As the evening unfolds, the group's dark confessions escalate—Ben shares a chilling story of how he took his best friend’s life during a hunting trip. Calvin recounts a harrowing car accident that claimed his wife’s life and led him to derive pleasure from the suffering of others, admitting to malpractice as a doctor. Leandro shares a meticulously plotted tale of poisoning a Triad leader over several weeks to leave no trace.
Meanwhile, The Man observes the meeting from a safe distance, armed with listening devices. He receives a call from Violet, played by Suki Waterhouse, who is on a potential killing spree.
When the group reconvenes after a smoke break, chaos ensues as Senator Kyle barges in, only to be shot. In a fit of rage, he confronts Joanna, accusing her of deviating from their original plan to merely intimidate him. The senator reveals suspicions that Joanna might be entangled with the CIA, which allegedly uses KA as a front for its assassination operations.
Alice, who claims to have received an untraceable message leading to the meeting, becomes a focal point of Joanna's suspicions. Joanna, adamant about Alice's connection to the botched hit, confronts her, while Molly inadvertently reveals her eavesdropping with a cough, which leads to an intense decision about her fate.
In a shocking turn of events, Joanna declares Alice the new leader of the group, sharing that she had made the initial attempt on the senator's life after Jade's failure. She reveals that Alice and Molly share a surname, Romanoff, indicating a supposed Russian affiliation. However, as the story unfolds, it becomes apparent that the sisters' connections may be as fabricated as the narratives spun within the walls of KA. As alliances shift, Alice and Molly leave with Krystal, eliminating the rest of the group, leaving behind a web of deceit where loyalty is as fleeting as life itself.
