On Tuesday night, an American exchange student in Hong Kong received an email from her university back in the States. “Urgent & Important,” read the subject field. It said that because of protests at the Chinese University of Hong Kong (CUHK)—where 20-year-old Sandra had been living since August—her safety was in jeopardy and “mandatory repatriation” was being enforced. In less than 24 hours, she and about a dozen other students from the same American university arrived at Hong Kong airport with their hastily packed suitcases.