Every age is certain its witches are real. The old world had servants of the Devil; later centuries had wreckers, subversives, and enemies of the people; we have our own quiet vocabulary for the ones we agree to destroy. This book argues that beneath these changing costumes lies a single machine—old, patient, and unnervingly consistent—that any frightened community can assemble from the same few parts and set running almost by reflex.

Traveling from the purification rituals of the ancient world to the accusation storms of the internet, Peter Kriger takes that machine apart piece by piece. He shows why persecutions ignite all at once instead of gathering slowly; why they refuse to stop even after the fear that lit them has burned away; why the decisive charge is always the one that no innocence can answer; why the informer is thanked and the defender endangered; and why the soothing arithmetic—only a handful are ever taken—is precisely the lie told to the one who is about to be taken.

Yet this is not a counsel of despair. Hunts do end, and there is a reliable way to tell an honest reckoning from a hunt that has merely borrowed its clothes. Humane, mordantly funny, and quietly alarming, this is a field guide to the oldest reflex in public life—and, for once, a clearly marked map of the exits.