The story revolves around the lives of two sisters, Joo Young and Joo Hee, who move into a new apartment. However, their seemingly ordinary lives take a nightmarish turn when Joo Hee mysteriously vanishes from their apartment without a trace. With mounting dread and an ever-present, disturbing noise in the background, Joo Young, and Joo Hee's boyfriend Ki Hoon embark on a harrowing mystery to find Joo Hee and uncover the source of the unsettling sounds.