So-yeon (Park Min-yeong) is a pet groomer who suffers from claustrophobia stemming from a childhood experience. One day, one of So-yeon's customers dies, leaving her cat Bi-dan behind. The mystery of the murder is unknown, and the cat is the only witness. As the police begin their investigation, So-yeon takes responsablilty of Bi-dan. But something strange happens to So-yeon from the day she brings Bi-dan home. Unsure of what is happeneing, So-yeon starts investigating the mysterious cat and the death of its owner.
