Human trafficking, including stealing and selling children, is widespread in China. The police are almost powerless to stop it, and corruption facilitates the trade. Desperate parents are joining forces to search for their sons and daughters. But their efforts are usually unsuccessful.

Guo Gangtang sells dried pumpkin gourds in Beijing's Yiwu City shopping center. The yellow containers are imprinted with historic figures, fairies or aphorisms - designs his wife finds on the Internet.

Business isn't going particularly well, partly because his stand is tucked away in a back corner, where the rent is cheaper. Guo rarely earns more than 1000 yuan (about €120 or $149) a month.

Out of pity, the landlord recently waived his rent. Fate has not treated Guo kindly. His child was stolen 13 years ago, and since then he has been motivated by only one desire: to find his son.

Whenever Guo, who is in his 40s, has saved enough money, he attaches two flags to the back seat of his moped and drives out into the countryside. The flags show a picture of a small boy, his son Xinzhen.

The day the world fell apart for Guo and his wife began like any other. He was living in a village in coastal Shandong Province, where he worked as a driver, transporting building materials on a tractor. It was Sept. 21, 1997. His little son Xinzhen, who was two-and-a-half years old, was playing with a girl from the neighborhood in front of the house door when a woman approached the children. The woman, a stranger, stroked the boy's face with a piece of cloth, eyewitnesses later reported. Then she turned slowly toward the street, which was about 100 meters (328 feet) away.