During her 18th birthday, the life of India Stoker is thrown into chaos following the tragic death of her beloved father, Richard, in a brutal car accident. This leaves her with her estranged and emotionally unstable mother, Evelyn. At the funeral, they meet Charlie, Richard's charming and world-traveling brother, who announces his intention to stay indefinitely to support the grieving family, a decision that is met with delight from Evelyn and a wary resentment from India.
As Charlie settles into their lives, tensions arise when India witnesses a heated confrontation between him and Mrs. McGarrick, the house's caretaker, who later mysteriously disappears. While Evelyn and Charlie grow increasingly closer, India resists his attempts to bond with her. The arrival of Gwendolyn, India's great aunt, raises further suspicions about Charlie's past when she questions his travel stories and hints to Evelyn that there may be more to Charlie than meets the eye.
One fateful night, Gwendolyn's paranoia leads her to change hotels, but Charlie tracks her down, cornering her at a payphone. He pretends to return her lost phone but brutally murders her with his belt, revealing the darker side of his charming facade. Meanwhile, India makes a shocking discovery of Mrs. McGarrick's body in the freezer, unfolding the gruesome truth—Charlie is a killer.
India's emotions spiral out of control, culminating in a violent act at school when she stabs a bully, Chris Pitts, in retaliation for his derogatory remarks about her mother. As she navigates her chaotic world, she encounters Whip Taylor at a diner, leading to a series of events where she aggressively bites him during an intimate moment. When Whip attempts to assault her, Charlie intervenes, killing him in a cold and calculated manner, further entwining India in his sinister web.
As she comes to terms with the disturbing reality of her situation, India finds herself both fascinated and repulsed by Charlie. She encounters disturbing truths after discovering a key to a locked drawer in Richard's office, where she unveils letters revealing Charlie's web of lies about his travels. Confronted with the dark history of her family—Charlie's murderous act against his own brother, Jonathan, stemming from jealousy over Richard's favoritism—India's emotions become a tumultuous mix of shock, betrayal, and ultimately, a bizarre sense of forgiveness.
Their relationship evolves into an unsettling intimacy, but once Evelyn uncovers the truth about Charlie, tension escalates. In a pivotal confrontation, Charlie attempts to strangle Evelyn, but India intervenes, fatally shooting him with a hunting rifle. After burying his body in the yard, India takes his car and heads for New York, where she has a fateful encounter with Sheriff Howard. When he pulls her over, India coldly expresses her desire to catch his attention and plunges garden shears into his neck, cementing her transformation into someone overcome by darkness. She then relentlessly pursues the wounded sheriff into the field, sealing her fate as she fully embraces her family's legacy of violence.
