A young woman finds herself in a confession booth where she encounters a mysterious employer and passionately requests to become his exclusive contract killer. To demonstrate her abilities, she boldly offers to eliminate his other contractors within just two weeks, asking in return for his assistance in finding someone for her needs.
Meanwhile, Bill (Simon Pegg) waits at a deserted metro station, where he is informed by the limping janitor Clinton (Mike Myers) that no trains will be arriving until 4:04 a.m. Finding Clinton's demeanor peculiar, Bill inquires if any freights are due. Clinton suggests he bide his time at a nearby café.
After failing to catch a train, Bill encounters petty thieves Lenny (Matthew Lewis) and Raymond (Thomas Turgoose), who threaten him. Displaying remarkable composure, Bill cleverly handles the situation without raising his voice, even attempting to purchase their unloaded gun.
Bill ultimately finds himself at an all-night diner where he meets Annie (Margot Robbie), a waitress with whom he engages in banter while trying to suppress a relentless cough, a symptom of his terminal illness. Bill shares his despair about the time he has left, explaining that his doctor can only offer comfort, not hope. Feeling a growing connection, he admits to her that he has a sense of déjà vu regarding their past interactions.
To his horror, Annie encourages him to consider the finality of his situation, urging him to take control of his fate by suggesting various gruesome ways to end his life. As their dark conversation unfolds, it becomes glaringly obvious that Annie isn't merely a waitress; she reveals herself to be a victim from Bill's past—someone he abused during his tenure as an English teacher at a residential school. A startling confrontation arises, leading to her stabbing Bill with his own pen and pushing him into an abandoned shaft.
In a concurrent plot, we rewind three weeks prior, where Annie is seen torturing Nigel Illing (Nick Moran), rendering him unconscious before mutilating him. Her rendezvous with her enigmatic employer, Mr. Franklyn, reveals a sinister hit plan involving his two hired guns—Vince ([Dexter Fletcher]) and Alfred (Max Irons). Tasked with retrieving a briefcase, they find themselves entangled in a series of events leading to a French strip club, where they encounter the alluring Bunny (who is, in reality, Annie).
As Vince and Alfred navigate their assignment, tensions rise when Vince is secretly offered double his pay to eliminate Alfred. This betrayal is cleverly orchestrated by Annie and Clinton. While complications unfold at an apartment filled with dire intentions, the waitress (revealed as a key player in this deadly game) confronts her former abuser, further intertwining their fates.
The climax unfolds with an intense standoff reminiscent of a sniper’s duel, where loyalties shift, and casualties mount as Annie takes vengeance on those who wronged her. The horror deepens as their father, Mr. Franklyn, is finally exposed for the monster he is, leading to the twins—Annie and her sister Bonnie—enacting their long-desired revenge against the man who shattered their lives.
In a shocking twist of fate, they find closure as they confront Mr. Franklyn and liberate themselves from the chains of their past, a cathartic resolution to a harrowing tale of survival and reckoning. Ultimately, the film leaves a haunting impression with themes of vengeance, betrayal, and the consequences of one’s actions reverberating through time.
