Violinist Xiaoying (played by Lu Shan) moved into a shared apartment with four bedrooms and a living room, and was warmly welcomed by the three tenants: the sissy fitness coach Lin Yu (played by Fu Heng), the "Weibo Internet celebrity" Mo Zheng (played by Song Hanhuan) and the socialite Wan Su (played by Wu Jinxi). The four seemingly different people get along well together, and the other three seem to have a particularly close relationship; however, after Xiaoying found a mysterious notebook, nightmares gradually invaded, and the thrilling records in the notebook reappeared in Xiaoying's life. Xiaoying began to have hallucinations and thought she was another person; through visits, she found that the owner of the diary was the previous tenant of her room, but died in a bizarre accident. More bizarre and terrifying events followed one after another, until a man who claimed to be her boyfriend appeared. Xiaoying seemed to find that she had another identity, and the entire shared house was shrouded in eerie and strange dangers...