Tang Huaibin, 55, is a detective of sorts, hunting clues to crack a mystery. But his is not a whodunit pursuit, but rather a quest to find the families of homeless people in Shanghai. Tang has become such an expert in his 21 years on the job that he always gets assigned the hardest cases at Shanghai Shelter, where he works. "This job involves a great deal of persistence, patience, attention to detail, love and experience," said Tang. "I patch together information and collect every detail, piece by piece, and then start over again if the information points in the wrong direction. Frustration is normal, but I never give up on any case." Every district in the city has a shelter, providing free meals, showers, accommodation and medical treatment for the homeless on a 24-hour, year-round basis. Officials from the shelters patrol the streets, asking those sleeping outdoors if they want to come to a shelter. No one is forced to go. Those who refuse are supplied with food and blankets. Since mid-December, when temperatures plunged below freezing, more than 800 people have checked into shelters, almost a third more than usual. Homeless people who appear to have no families to care for them usually get referred to Shanghai Shelter. Not all of them want to be reunited with families, but many — especially those who are older — are willing. Last year, the Shanghai Shelter received 2,583 people — about 27 percent of them disabled or with mental disorders. Some 47 homeless people who had lost contact with their families received help finding their families, according to the Shanghai Civil Affairs Bureau. In the past three years, Tang has had a caseload of more than 100 homeless people. Prior to that, the shelter wasn’t keeping count. Some of Tang’s “clients” lost contact with their families up to 50 years ago. Shelter officials use a variety of methods and technologies to identify the homeless, including facial recognition, DNA matching, recognizing accents and dialects and help from local officials and the media. It’s by no means an easy job. "Some of the homeless have mental problems," said Kang Qingping, deputy director of Shanghai Shelter. "Others left home so long ago that their memories of family fade. Some don’t want to recall their pasts because of psychological traumas. Some have had their residency permits revoked. All of these factors feed into the challenge of trying to reunite them with families." When the hunt begins, the way forward is blackness and thorns, Tang said. "In many cases, their memories are blank for various reasons," said Tang. "But as long as there is a ray of hope, I never give up." He added, "When reunions occur, their relatives sometimes don’t even recognize them at first because of so many years of lost contact. Then they burst into tears of joy, which makes me feel my efforts are all worthwhile." Cases that seem dead in the water are often reopened if new clues are found, he said. One of the homeless, identified by the pseudonym Qu Changshun, recently boarded a train from Shanghai to the city of Luoyang in Henan Province to be reunited with his family after 40 years. Qu, 63, checked into the Baoshan District Shelter in late December to escape a bitter cold front. He initially refused to communicate, give his name or offer any information about his family. After initial efforts to find his relatives failed, Tang was called in. Based on his accent, Tang identified Qu's hometown, and more details gradually began to emerge. "Because of psychological trauma, he was not willing to talk at first," said Tang. With gentle but persistent prodding from Tang and his colleagues, Qu gradually opened up. He told them he left his hometown in the late 1970s because of a failed relationship. With the help of Luoyang police, Tang's staff eventually located Qu's family. Despite the long separation, Qu and his younger brother recognized each other immediately during a video chat arranged by the shelter and burst into tears. Qu was told his family searched for him for many years and that his father died, in part due to grief over his son’s disappearance. His mother is now 86 and suffers from heart disease. "We never gave up hope over the years that you would return someday,” his brother said. Tang was in the army and then worked at a hospital before taking his current job. "My colleagues came from across China, speaking diversified dialects,” he said. “That’s how I learned to recognize many accents.” Tang said his interests include history, culture and geography. He keeps up on regional cuisine and customs, and reads a lot of books. In short, he can draw on eclectic knowledge to track down the origins of homeless people. About 80 to 90 percent of the homeless in Shanghai are from Henan, Anhui, Jiangxi, Shandong, Yunnan, Guizhou, Sichuan and Hubei provinces, he said. Tang speaks eight major dialects but notes that one dialect can vary from place to place. "Dialect is the most important way to identify a person,” Tang told Shanghai Daily. "Most homeless who lose contact with their families a long time ago are now in their 60s and 70s, but it’s difficult to change your accent." Tang is full of stories about his work. Like the 2005 case of a 6-year-old boy that took him three years to crack. The boy spoke Sichuan dialect. "He provided very limited information — fleeting memories of his parents, taking a train, riding a tractor, climbing a mountain, living in a village with a playground, butcher and small shop,” said Tang. "He couldn’t remember anything else, and his accent covered a large area.” Tang and his colleagues contacted villages one by one, asking about a lost child. They finally narrowed the search down to one village, and the Party secretary there visited all residents. It turned out that the boy was adopted, and his parents were migrant workers moving from one place to another in Jiangsu Province. They had taken the boy home to Sichuan only once. The shelter in Minhang District once received a 57-year-old homeless man surnamed Xu, who had two disabled hands and burns on his face. He couldn’t tell shelter staff his name, address or any information about his family. "The man had a very strong accent and could not read or write," said Tang. The identification process was complicated and took about a month. “Xu's memory was patchy,” Tang said. “But we kept chatting with him trying to piece together fragments of information about his life.” Xu could remember vaguely that he had worked in a coal mine. "Because his memory was so clouded, he sometimes gave us wrong information, leading us down a blind alley,” Tang said. "It was like fishing for a needle in the ocean, but we did not give up." Numerous maps were checked and local authorities contacted until one day, a relative from Lebang Village in Guizhou Province told officials that the man might be his brother-in-law, who had been missing for years. It turned out Xu's parents died in his childhood and he was raised by an aunt. A woman who turned out to be his younger sister said Xu left home when he was 15 and the family had never given up looking for him, though their means were limited. In another case, Tang helped a wheelchair-bound man who had lost contact with his family 50 years earlier in Henan Province. "You have to have a sharp ear when listening to these people talk or you might miss a critical clue that they might not repeat again,” said Tang. "For people who have mental problems, you tend to grasp clues when they are talking about something that interests them.” It is even more challenging for people without language functions. In trying to communicate with a homeless man suffering from cerebral paralysis, who could not talk or write, Tang extracted information from him through gestures and eye motions. Tang finally narrowed the scope of his origins and 3,000 names were checked before his family was found. After the man was finally identified, his son drove two days to Shanghai from the city of Jiaozuo in Henan Province. "His son had been looking for him for more than 20 years, but he didn’t recognize his father at first,” Tang said. "DNA confirmed their relationship. The son knelt down to thank us. It brought tears to my eyes." Tang has been teaching his detective techniques to younger workers before his retirement in five years. A team of 20, with an average age of about 30, works with him. "Without persistence, patience and a loving heart, people cannot do this job well," Tang said. "All clues linger in my mind when the families are not found, and often I suddenly have an intuitive thought and all the clues fall into place.”