In a country that only tolerates dissent in small doses — and relies on property as its economic growth engine — a mortgage boycott by hundreds of thousands of middle-class Chinese has become a five-alarm fire for authorities.

It began with a 590-word letter penned by angry purchasers of the half-built Dynasty Mansion project in Jingdezhen, Jiangxi province, whose pleas for China Evergrande Group to complete homes they’d long been paying for had fallen on deaf ears. "All homebuyers with outstanding mortgage loans will stop paying,” unless construction resumes before Oct. 20, they threatened.

The ultimatum raced across social media platforms WeChat and Douyin, becoming a call to action for those caught out by China’s rapidly deflating property bubble. Within days, the letter became a template for protests from Shanghai to Beijing, and Shenzhen to Zhengzhou, with homeowners cutting and pasting from it to draft their own boycott manifestos.