In the haunting town of Salem, Massachusetts, renowned for its dark history of witch hunts and trials, the story revolves around the Fletcher siblings—Billie Fletcher, Marcus Fletcher, and Jo. Their father left when he sobered up, leaving them under the care of their mother, while their Uncle Bob has been living with them for years, unemployed and somewhat peripheral to their lives. Billie, the most social of the siblings, enjoys a lively social life, whereas Marcus is more of a lone wolf, often keeping to himself. Jo, who is close to Marcus and considers him his only friend, spends much of his time with him. Their bond is emphasized through their shared activities, like cycling through the woods, which leads to a chilling discovery.
One day, during one of their rides, Jo hears mysterious voices whispering his name as they approach an abandoned cabin. Curious yet cautious, Jo and Marcus venture inside and stumble upon a suspicious knife and an old diary. Marcus immediately dismisses the cabin as the lair of a dangerous psychopath who might be toying with their minds, convincing Jo to leave the ominous place behind. Despite their retreat, Jo keeps the sinister, rusted knife with him, unaware of its cursed nature. The knife has inscriptions that read, "I will play, I won't quit," a phrase that Jo naively reads aloud, unwittingly unleashing a malevolent force.
Soon after, Jo begins to act strangely—sweating profusely and seemingly under the influence of a demonic voice. As the entity takes hold of him, Jo persuades Billie, her boyfriend Pete, her best friend Sophie, Marcus, and Uncle Bob to participate in a sinister game. However, the situation spirals out of control when Billie, Pete, and Sophie leave to attend a party, leaving Jo behind. Jo forces Marcus to repeat the curse inscribed on the knife, whispering, >"Tell me, demon, am I it?"<. In that moment, the demonic spirit possesses Marcus, transforming him into an instrument of chaos and violence.
As Marcus's body becomes a vessel for the evil force, he embarks on a killing spree, playing deadly games with his victims. His initial target is Uncle Bob, whom Marcus chokes to death during a game of Hangman. With his mind consumed by the demon, Marcus moves on to attack others, including victims at a party attended by Billie, Pete, and Sophie. Marcus’s transformation is horrifying to witness, marked by carving an 'X' symbol on his forehead and blood streaming down his face. The demon relishes in torment, demanding more victims to entertain him with hide and seek, while Marcus's actions become increasingly vicious and unpredictable.
Billie, realizing the grave danger, encounters Jo on the way back from the party. He informs her of the murderous rampage, prompting Billie, Sophie, and Jo to investigate the old cabin again. Their search uncovers a shocking revelation—the diary records a tragic history of a woman accused of witchcraft and her son, Daniel, who endured horrific torture. The mother, faced with relentless harassment and violence from her town, fled into the woods, where her son was eventually captured by children. These children tricked Daniel into playing games, carving the same cursed 'X' symbol on his forehead as a mark of torment. They subjected him to inhumane torture—ripping teeth from his mouth, hanging him from a tree, and finally torching his body—an atrocity that led the mother to turn to witchcraft, creating a cursed knife from Daniel’s bone.
This curse allowed Daniel's spirit to rise repeatedly, possessing vessels and forcing victims into sadistic games, much like the ones inflicted upon him in life. The story of Daniel's vengeful curses is dark and haunting, revealing that only by ending the curse—by destroying the vessel—could the torment be halted. Billie refuses to accept that the story of Daniel's revenge might be over, clinging to hope that they can break the cycle.
Desperate to free Marcus from the demon’s grip, Jo engages in a game of flashlight tag with the possessed Marcus and Daniel's spirit, ultimately managing to weaken Marcus as Jo's flashlight targets him and causes his body to catch fire. Together, Billie and Jo fight to weaken the demon, with Billie seizing the cursed knife and attempting the final ritual. In a harrowing confrontation, Daniel tries to seize control of Billie, but she fights back fiercely, stabbing him in the eyes with her thumb to break his hold. As she pulls him back into reality, Marcus and Jo work together to suppress the spirit's influence.
The climax reaches its peak as Daniel, now fully in control, approaches Jo, offering to take over his body. Jo bravely stabs Daniel in the stomach with the cursed knife, causing his now corporeal form to disintegrate into a black, liquid puddle on the floor. With Daniel defeated for the first time in his vengeful existence, the immediate threat ends. The following morning, Marcus turns himself into the police, plagued by guilt and unable to explain the true nature of the crimes, knowing that revealing the supernatural truth would seem insane.
In a grim but open-ended finale, the cursed knife reappears at the cabin, hinting that the evil might not be entirely vanquished. The story leaves viewers with a chilling reminder of how the dark history intertwined with the cursed artifacts continues to haunt those connected to it, and the ongoing threat of unleashed evil, even after apparent victory.
