The beautiful girl So Yeon (played by Park Min-young) has been troubled by claustrophobia for many years. As long as she stays in a confined space, she will feel great depression and terror. Fortunately, the cute and naughty little animals soothed her fragile heart. Now So Yeon works as an animal makeup artist in a pet shop and lives a plain and happy life. But her life was soon broken by an accident. One of her guests died in the elevator shortly after leaving, and So Yeon had to temporarily help her take care of her pet cat Xiaobu. From this moment on, she often saw short-haired little girls with gloomy faces everywhere. Her spirit was almost collapsed, but the strange things intensified, and eventually even her good friend Bo Ji died tragically for no reason. So Yeon vaguely felt that all the terrorist incidents that had happened so far were related to the mysterious Xiaobu...