In a gripping flashback at a diner, 12-year-old Sam learns that her assassin mother, Scarlet, is fleeing the scene after a botched job. As armed men arrive to eliminate Scarlet, she fights back and escapes, leaving a devastated Sam behind. Fast forward fifteen years, and Sam has become an assassin herself, working under Nathan, who oversees the same organization where Scarlet once thrived. Nathan assigns Sam a perilous task: eliminate a man who has embezzled funds from The Firm and reclaim the stolen money.
Disguised as a librarian, Sam heads to a weapons armory to procure new tools for her job. There, she encounters three of Scarlet's former associates: Anna May, Madeleine, and Florence. Initially, they consider killing Sam for intruding but change their minds upon recognizing her identity, ultimately providing her with clean weapons.
During her mission, Sam infiltrates a hotel room to reclaim the stolen cash, only to fatally shoot the man involved when he lunges for his ringing phone. Listening in reveals a shocking twist: he had taken the money to rescue his kidnapped daughter, Emily. Determined to save the girl, Sam drives the injured man to a private doctor associated with the firm. When Nathan learns of Sam's intentions, he dispatches three henchmen to thwart her plans, but she swiftly neutralizes them. In a tense climax, masked assailants deliver Emily before retreating with the money, though chaos ensues, resulting in the deaths of the attackers and the loss of the stolen cash.
Simultaneously, Nathan uncovers that one of the slain henchmen was the son of Jim McAlister, a powerful crime lord. Seeking to avoid an escalation, Nathan betrays Sam by providing her location to Jim. As Sam seeks to reunite Emily with her father, they discover he didn't survive the ordeal. The doctor's office soon turns into a battleground when Nathan's henchmen arrive seeking revenge. Injected with a paralysis serum, Sam ingeniously rigs a knife and a gun to her hands with Emily's help, ultimately dispatching the henchmen.
Fleeing in her car with Emily at the wheel, Sam receives a text from Nathan, leading them to a safe house for supplies. There, a surprise encounter with Scarlet reveals that she has kept tabs on Sam over the years. As the henchmen close in, Scarlet guides Sam and Emily through a covert escape. Returning to the library, tensions rise when the librarians challenge Scarlet for her years of silence. Just then, gunmen attack; Sam fights valiantly but struggles until Scarlet intervenes to save her. The librarians decide to join the fray, resulting in a fierce battle that leaves all assailants dead except for Virgil, Jim's nephew, who kidnaps Emily and calls Sam to a diner for a trade—her surrender for Emily's safety.
Sam confronts Jim, who reveals his inability to relate to women, intending to torture her in front of Emily. Just in the nick of time, Scarlet, Anna May, and Florence launch a surprise attack, allowing Sam to escape with Emily before Jim and his crew meet their end. In a poignant moment later, Sam expresses her remorse for the death of Emily's father, but Emily forgives her. Disguised as a Girl Scout, Emily confronts Nathan, threatening his life to force him to retract the hit on Sam. The film concludes with Sam, Emily, Scarlet, Anna May, and Florence driving down the coast together, embarking on a new journey.
