Cheng Fei, an 18-year-old motherless boy, was raised by his father and grandmother. In the summer vacation of 2007, Cheng Fei found a missing person notice in his father's room, but the missing person was his two-year-lost netizen "Swallowtail Butterfly", He Sheng. Cheng Fei pretends to be a tenant and stays at the home of He Sheng's mother, He Xiuqing, but accidentally uncovers the inextricable relationship between the mother and daughter and himself. The mysterious He Sheng disappears, Cheng Jianguo buries his lies, and the eccentric He Xiuqing is a loner. In the fog of two families' past, Cheng Fei gradually approaches the truth that has been sealed for many years. ......