Bundled against the cold, the businessman made his way down the steps. Coming toward him in blue mittens was a middle-aged woman.

"Do you know that we're going to take a stroll this weekend?" she whispered, using the latest euphemism for the unofficial protests that have unnerved authorities in Shanghai over the past month.

He nodded.

Behind her, protest banners streamed from the windows of high-rise apartment blocks, signs of middle-class discontent over a planned extension of the city's magnetic levitation, or maglev, train through residential neighborhoods.

The couple checked to make sure no plainclothes police were nearby and discussed where security forces had been posted in recent days. "Did you take any photos?" the man asked. Yes, she said, promising to send them to him so he could post the evidence online.