In the summer of 2015, as Memphis exploded with protests over the police killing of a 19-year-old man, activists began hearing on Facebook from someone called Bob Smith. The name was generic, and so was his profile picture: a Guy Fawkes mask, the symbol of anti-government dissent.
Smith acted as if he supported the protesters, and, slowly, they let him into their online community. Over the next three years, dozens of them accepted his friend requests, allowing him to observe private discussions over marches, rallies and demonstrations. In public postings and private messages he described himself as a far-left Democrat, a “fellow protester” and a “man of color.”