Hee-yeon Hae-yeon Kil, Min-ho Hyuk-kwon Park, and their little daughter Joon-hee Jun-hee move to Mt. Jang with Joon-hee’s senile grandmother, hoping a change of scenery might help them heal after their young son vanished five years ago. The grandmother begins to hear her dead sister’s voice calling from the woods, a haunting thread that slowly ties the past to the present.
Two children arrive in search of their dog, the same dog involved in the car accident that opened this terrible trail. The kids hear the dog’s bark and follow it to a brick wall, where a little girl Rin-Ah Shin is pulled through a hole by an unseen force, only to escape at the last moment. The danger feels closer than anyone wants to admit, and the sense of being watched intensifies as night falls.
The children run to Hee-yeon and Min-ho for help. Hee-yeon encounters a little girl in the woods but is drawn away by the kids and her husband, who enters the hole and discovers a bolted door. When he opens it, a mutilated woman falls through, dead, a grim omen that marks the beginning of a string of unexplained events. They report it to the police, hoping for answers they can’t yet name. That night, the mysterious girl appears at their door, and Hee-yeon takes her in. The girl calls her “Mom,” imitates Joon-hee’s voice, and insists that her name is also Joon-hee, a chilling parallel that unsettles the family and unsettles the balance they’ve been trying to maintain.
Hee-yeon discovers signs of abuse on the girl’s body, and Min-ho grows ever more unsettled by the child’s presence and Hee-yeon’s unwillingness to move on from their son’s disappearance. The police track down the man from the beginning, who now hears voices and has eye problems, and he is killed by the entity. The detective, Yul Lee, uncovers that Mt. Jang is home to many missing persons cases, all of which began with people reporting voices of dead loved ones before vanishing. A faded old photo from the 1980s shows a man with the same little girl Hee-yeon has taken in, tying the present to a long, dark history of need and harm.
The grandmother tapes over the house’s mirrors because that is how the entity slips through, and she follows the voices she hears to a cave behind the brick wall. Min-ho goes to search for her and disappears as well, leaving Hee-yeon desperate for a sign. She seeks help from a neighbor, a blind woman who explains that a shaman once lived nearby, and that his daughter — the same girl now haunting Hee-yeon — became bound to a malevolent spirit living in Mount Jangsan, the Jangsan Tiger. The shaman’s abuse, possession, and the spirit’s hunger have cursed both him and his daughter, who mimic voices to lure victims and sacrifice them. The neighbor warns Hee-yeon not to trust the little girl, for those who yield to the voices lose their sight.
Jangsanbum attacks Joon-hee; Jangsanbum’s daughter saves her. Hee-yeon locks Joon-hee in her room, warning her not to trust any voices and to call the detective if she does not return. Hee-yeon then asks Jangsanbum’s daughter to guide her to Min-ho. In the cave, they are chased into an area full of mirrors, and Hee-yeon is overwhelmed by the chorus of voices until Min-ho, now blind, shatters the largest mirror that houses the spirit, destroying both the spirit and the shaman. Hee-yeon, weakened by the little girl’s mimicry of her missing son’s voice, goes blind. At the cave’s opening, unable to resist the voice of her son, Hee-yeon turns back despite Min-ho’s pleas that it is not their son. She returns to the little girl and they descend back into the cave, while Min-ho stumbles outside and is found by the detective.
