For one week in early 2015, China was riveted by a former news anchor's self-financed online documentary about air pollution.
Speaking gently in the film, Chai Jing described her newborn daughter's surgery to remove a tumor, and her own sudden terror about China's polluted air. She began wearing a mask. At home, she taped the cracks in doors and windows. She kept her daughter indoors half the time, "like a prisoner."
Smog is something everyone in China is accustomed to, but Ms. Chai's "Under the Dome" reminded people how personal the problem is, and how visceral. Her documentary was a folksy mix of interviews, animation, research and her own stories. State media covered the viral phenomenon; the environment minister praised it.
But a week after the documentary went online, it disappeared from China's internet. Perhaps overwhelmed by the response, propaganda authorities had ordered portals to delete it.
But by then more than 200 million people had already watched.