The film ends with Monkey and his friends reuniting as adults. Two months later, Mi Lan and Monkey's former friends stop hanging out with each other and they each go their own separate ways. Monkey's friends ostracize him after he attempts to rape Mi Lan in her apartment. After Monkey introduces Mi Lan to his friends, she becomes a part of their group, and despite Monkey's feelings for her, Mi Lan falls for Monkey's friend, Liu Yiku (Geng Le). Monkey befriends her and they occasionally spend time together.
He spends his days in the vicinity of her home, and when he finally spots Mi Lan on the streets, he strikes up a conversation with her. After randomly entering Mi Lan's apartment, Monkey sees a photo of Mi Lan smiling in a swimming suit and becomes deeply attracted to her.
Monkey has a homemade skeleton key which he uses to sneak into people's apartments during his free time. Most of the story happens during the summer and revolves around Monkey's dalliances, his friendship with a group of roguish boys, and his subsequent angst-filled crush on an older girl, Mi Lan ( Ning Jing). It is told from the perspective of Ma Xiaojun, a teenage boy nicknamed "Monkey" (played by Xia Yu, some of Monkey's experiences mimic director Jiang's during the Revolution), Monkey and his friends are free to roam the streets of Beijing day and night because the local school system is non-functional and the Cultural Revolution has caused their parents to be either busy or away. The film is set in the early 1970s in Beijing, during the Cultural Revolution.