But even before an economic slowdown, another kind of strain is beginning to show: some of China's well-to-do are starting to decouple rising incomes alone from a rising sense of well-being. In recent years, growing fears about food safety (contaminated milk-powder for babies; exploding watermelons) and dangerous infrastructure (a high-speed train crash; collapsing buildings), among other concerns, have provoked public outcry and Internet maelstroms criticizing the government. In the minds of at least some Chinese urbanites, especially young parents, such worries are beginning to outweigh the appeal of a yet larger apartment or flashier car. Even for those who don't go so far as to conclude, as the activist-artist Ai Weiwei recently wrote in Newsweek of Beijing, that their hometown is a "nightmare city," the belief that rising GDP alone brings contentment and security is coming under question.

Or at least, that's what I was told by anxious Dalian citizens who joined the Aug. 14 protest.

On that drizzly Sunday morning, a throng of residents had packed the downtown People's Square, opposite Dalian's City Hall, some carrying hand-made placards that read: "Get out PX! Give us back the environment! Give us back Dalian!" It was one of the largest protests reported in China in the past decade. Remarkably, the city's top two officials, the mayor and the party secretary, quickly promised to relocate the factory. Cautious Dalian residents have taken those pledges with greater skepticism than much of the international media (which soon declared a victory for "people power"). They are now watching closely to see what happens next.

The chemical PX, manufactured at the Dalian-Fujia factory, is used to make polyester. The plant had not been linked to significant existing health problems in Dalian, but residents feared that a future tropical storm might rupture its chemical storage tanks, which are located near the coast, and inundate the city with toxic floodwaters. The protest came a few days after a real storm, Typhoon Muifa, had grazed the nearby coast, raising online discussions of a series of terrifying "what if" scenarios. Anxious predictions, as well as an anonymous online call to march on People's Square, had circulated through social media sites in the days before.

When I arrived in Dalian the following Tuesday, several people spoke with me about why they'd marched that Sunday, although most asked that their full names not be used in print. Typhoon Muifa, and the distress it whipped up, was clearly the immediate cause that led to the demonstration, but there was something else on their minds, too. Now, at last, they had cause to put a name to it.

And it was this: the surprising and chilling conviction that Dalian's best days were behind it. The prosperous city, their city, had seen its golden age come and go. Now daily life was more strained, and the city itself was literally falling apart. "Dalian used to be one of the most beautiful and great cities in China," one university professor told me. "But now things are all downhill." It's not that this despair caused the protest, but it contributed to an atmosphere of tension that proved highly flammable when the right match was lit.