Klara serves as an interpreter in the French Army during Opération Chammal in Syria. Her life takes a harrowing turn when she witnesses a suspected terrorist's young son detonate explosives concealed on his body, an act instigated by the father. The traumatic blast leaves her reeling, and she begins suffering from debilitating migraine headaches. As a result, Klara returns home to Nice, where she lives with her mother, Maria and her sister, Tania, while participating in counter-terrorist operations under Opération Sentinelle.
While on patrol, Klara's psychological scars manifest through increasingly impulsive and violent actions towards potential suspects. The prescribed painkillers are insufficient, leading her to seek additional medications through illegal means. One fateful night, Klara and her sister Tania visit a nightclub. As Tania mingles with a group of Russians, Klara maintains a watchful eye. After a night of dancing, Tania signals that she is leaving with them.
Tragically, the following day brings devastating news: Tania has been brutally raped and left in a coma. Klara, enraged and desperate for answers, takes it upon herself to investigate the crime. Diving into the club’s security footage, she identifies the man accompanying Tania. This suspect is revealed to be Yvan Kadnikov, son of the powerful Russian tycoon, Leonid Kadnikov. With both of them holding diplomatic immunity, Klara finds herself thwarted in her pursuit of justice.
Determined to confront Yvan, Klara tracks him down at the nightclub. During their encounter, Yvan denies any involvement with Tania, but soon enough, his friends intervene, resulting in Klara being forcibly removed. Undeterred, she infiltrates Leonid's villa to find Yvan but is captured by his formidable bodyguards. During a chilling confrontation, Leonid brazenly admits to the crime, claiming his son is uninterested in women. He then attempts to eliminate Klara by leaving her to drown, but her fierce determination enables her to escape.
As Tania eventually awakens from her coma, she chooses not to press charges, much to Klara's dismay. Outside her sister’s hospital room, Klara learns from a news report that Leonid plans to return to Russia. Shortly thereafter, a suspicious embolism strikes Tania, leading Klara to suspect foul play. She confronts and defeats the assassin responsible, who is linked to Leonid.
Consumed by a thirst for vengeance, Klara stealthily acquires weapons from her unit's armory and infiltrates Leonid's estate. After dispatching the guards, she confronts Leonid, who attempts to bribe her. In a fierce struggle, Klara pushes him over a bannister, believing her mission to be complete. However, in a twist, Yvan manages to stab her fatally, although she reacts instinctively and fatally shoots him.
Wounded but resolute, Klara escapes as law enforcement closes in. The story takes a suspenseful turn three months later when Leonid, recovering in his luxurious Dubai hotel, unwittingly faces Klara, who has disguised herself as room service. Driven by revenge, she brutally stabs him with a fork in a startling act of retribution. Now a fugitive, Klara silently checks on Tania from afar, witnessing her sister's recovery as she resumes her life with friends. With a heavy heart, Klara retreats into the shadows, forever marked by the traumatic events that have unfolded.
