Winter is just about to start in a small town in southern China, when Lynn (16), a 'left-behind' child who grew up with her grandparents, prepares to take the high school final examinations. Her mother, who works in faraway Guangdong as a long-time migrant worker, wants her to get into a police academy. But Lynn's preparations are not going well. At school, she is bullied by her classmates, while at home three cousins never stop teasing her. Her friendship with May, who attends another high school in town, is her only outlet. May doesn't like taking care of her disabled brother, and the girls often escape from their family homes to spend the night at a Net Cafe. After a girl at May's high school is raped and killed, May's foster mother confiscates her phone. When Lynn has to guard the phones of her classmates, she steals a phone of a girl who has bullied her and gives it to May. May encourages her to steal more phones, which they then sell cheaply. They spend the money on getting their hair done, and have a nightly meal with the hairdressers. Lynn is made drunk, and when she wakes up she can't find May. After this incident, May stops answering Lynn's calls. By herself, Lynn continues the risky path of selling stolen phones. She meets Dawei, a boy from the same school. As she comes to rely on this son of a police bureau chief, she slowly forgets May. Then Lynn's mother suddenly makes a trip home to borrow money from relatives and friends. When she sees how Lynn is changed, she decides to investigate her lower body... Mother's discovery leaves Lynn confused. Who was it?