Julian, an American expatriate, operates a Muay Thai boxing club in Bangkok, Thailand, alongside his older brother, Billy, using the establishment as a front for their illicit drug trade. Quiet and enigmatic, Julian carries the weight of a troubled past. He engages in dark and deviant sexual practices, often finding pleasure in watching his favorite prostitute, Mai, as she masturbates while he prefers to be bound.
One fateful night, Billy commits a gruesome act by raping and killing an underage prostitute, drawing the ire of the Thai police. The Lieutenant, Chang, permits the girl's father, Choi Yan Lee, to take revenge on Billy in whatever manner he deems fitting. Choi mercilessly beats Billy to death in the very room where his daughter met her fate. However, Chang, enforcing the law his way, punishes Choi by severing his forearm as a consequence for allowing his daughter to descend into prostitution.
In the aftermath, Julian has unsettling visions. During an encounter with Mai, he envisions a disturbing meeting with Chang in a dimly lit room, where Chang inflicts severe physical punishment upon him—cutting off his hands. When Julian learns of his brother's tragic murder, he confronts Choi at his kiosk. Nevertheless, compassion leads Julian to spare Choi's life, despite the tumultuous emotions surrounding the situation.
Once Julian's mother, Crystal, arrives in Bangkok, she demands urgent retribution for Billy’s demise. Yet, Julian refuses to carry out vengeance against Choi, believing it was a justified act driven by a father's grief. This defiance infuriates Crystal. After orchestrating Choi's murder, Crystal discovers Chang's deeper involvement and initiates a meeting with rival drug dealer Byron, proposing a partnership in exchange for eliminating Chang.
As the police investigate Choi's death at Julian's establishment, Chang dismisses Julian as a suspect. However, Julian feels an inexplicable connection to Chang, recalling him from his ominous visions. He follows Chang but loses him in the labyrinth of Bangkok's nightlife. That evening, Julian attempts to introduce Mai to Crystal as his girlfriend, but she quickly pierces through the facade. Crystal belittles both Mai and Julian, even claiming he lacks the virility of his deceased brother. Julian’s frustration culminates in an act of vicious humiliation towards Mai on their way back from dinner.
Tensions escalate when two assassins on motorcycles attempt to eliminate Chang at a restaurant, leading to chaos andbloodshed. Chang proves formidable, swiftly eliminating one assassin while pursuing the other. After a relentless chase, the surviving hitman reluctantly reveals his boss, Li Po, who is driven to crime for the sake of his disabled son. Chang, displaying unexpected compassion, spares Li Po’s life but takes down the remaining gunman.
Driven by anger and revenge, Julian confronts Chang at his boxing venue, but the experienced Chang outmatches him effortlessly. Following the bout, Crystal realizes Chang suspects her of orchestrating the hits on him. In desperation, she begs Julian to kill Chang, reminiscent of her previous pleas involving his father. She tantalizes Julian with promises of returning to a nurturing role in his life, igniting a flicker of hope within him.
Julian, alongside his accomplice Charlie Ling, plots an invasion into Chang's home after taking out his guard, fueled by his mother’s commands. However, moral complexities arise when Charlie decides to kill Chang’s daughter, and in a moment of reckoning, Julian eliminates Charlie before he can commit the atrocious act.
Meanwhile, Chang finds Crystal and punishes her with brutal efficiency for her manipulations. He coldly chooses to cut her throat, cementing her fate. When Julian returns to the hotel to find his mother's lifeless body, he is left in a daze. In a haunting act of mourning, he makes a visceral connection by cutting open her abdomen and placing his hand inside.
The film reaches its chilling conclusion as Julian is seen together with Chang in a field, where tension culminates in a brutal moment of finality with Chang severing both of Julian's hands. As the credits roll, Chang is illustrated passionately singing in a karaoke club, surrounded by fellow officers, leaving an eerie silence in his wake.
