The firm subjected the finalists to another round of interviews and psychological evaluations. Barely two months after the search began, Mr. Big received thick dossiers on each of the eight, with detailed information about their families and finances, habits and hobbies, and physical and mental conditions.

Finally, a series of grainy videos landed in his e-mail in-box. The first showed the top three prospects from Chengdu, sitting and standing, walking and talking, smiling and laughing. One of them, a demure 24-year-old with long black hair and black hot pants who seemed poised in front of the camera, was the graduate student whom Ms. Yang had pursued on a hunch at Master Kong Chef’s Table.

Ms. Yang’s hunting skills and tenacity had paid off again, giving her two of the eight finalists, and a 25 percent chance of winning the bonus of $32,000. (For finding two of the top 20, she had already earned a share of a smaller bonus.) When I asked about the reward, Ms. Yang demurred at first. “My aim is just to find a match that makes both people happy,” she said, before adding: “Inside my heart, I want my girls to win.”

Ms. Yang has worked hard for the chance. She heads to her job early in the morning and returns after 8 p.m., leaving her 5-year-old son in her mother-in-law’s care. She is often gone for weeks at a time on love-hunting trips. Her husband, whom she married at 22, when he was 35, ran a trucking logistics company that folded in 2009. Since then, he hasn’t worked much. With one large bonus, Ms. Yang bought him a Mitsubishi car that he tinkers with. Her occupation has given her a rather jaded view of the prospects for career women like herself. Once she told me half-jokingly: “It’s a good thing I’m already married. I would never stand a chance.”

Mr. Big’s Choice

In June, Mr. Big flew to Chengdu for meetings with the three local finalists. Riding an elevator to the lobby of the Shangri-La Hotel, he fidgeted nervously with the part in his moussed hair. He had invested more than a half-million dollars in the search, and was about to see if the money was well spent.

His final date in Chengdu was with the Zhou Tao look-alike whom Ms. Yang had approached at the noodle restaurant. At first, it seemed a mismatch, and not just because of the 18-year age gap. He knew nearly everything about her — her dating history, her recent acceptance to a graduate school, her father’s lofty government post — while she knew little more than his height and weight. She didn’t even know his name. Diamond Love had told her only that his net worth exceeded $800,000.

The young woman tried to keep things casual by taking him to a local Sichuanese restaurant. But Mr. Big insisted on bringing along a female consultant from Diamond Love and sitting awkwardly off to one side during the meal. According to the consultant, Li Minmin, he sat in this position “to better evaluate her profile, her skin, and her teeth.”