Xiuzhi, 17, is about to board a plane with his father, who has come from the US to take him back to further his education. His father had originally moved there when Xiuzhi was only 11 months old, but Xiuzhi's mother, Tian Guifang, had insisted on staying in China to look after their son. It had soon became clear that Xiuzhi was not an ordinary child: he lived in his own world, was precociously intelligent, and was always causing trouble at school due to his inability to get on with other kids. Even while having his tonsils removed one day, he ran off halfway through the operation and hid until Guifang found him. Eventually it was confirmed that Xiuzhi had Asperger's Syndrome, and Guifang offered to do menial jobs at the kindergarten in order to help the staff to look after him. By the age of six, when he went to primary school, Xiuzhi was already super-intelligent, with a ruthlessly logical, mathematical mind. Guifang found comfort in a close friendship with Li Yahui, a travelling businessman with whom she slept when he was in town; but when he suggested transferring Xiuzhi to a school in Tianjin, Guifang rejected the idea. As a devoted single mother, she worked round the clock to support Xiuzhi, though he never seemed to appreciate her efforts. When she was laid off at at work, Guifang was faced with the further challenge of making economies for the two of them to survive.