The black diary is passed between strangers, carrying the secret thoughts of different people: a job seeker framed a love rival for his crush, causing the other person to drop out of school but confess out of guilt; hairdresser Xu Xiaoyan was teased by a colleague, set up a trap for revenge, but encountered an unexpected horror; Hu Xiaolai, a middle school student, sent ambiguous text messages as a joke, which caused a conflict between his parents and even injured his father. The beautiful writer who finally received the diary processed the secrets into a story, but after submitting the article, she received a red warning of "death to those who leak the secrets", implying that the danger continues.
