The arsons started on a cold November midnight and didn't stop for months. Night after night, the people of Accomack County waited to see which building would burn down next, regarding each other at first with compassion, and later suspicion. Vigilante groups sprang up, patrolling the rural Virginia coast with cameras and camouflage. Volunteer firefighters slept at their stations. The arsonist seemed to target abandoned buildings, but local police were stretched too thin to surveil them all. Accomack was desolate--there were hundreds of abandoned buildings. And by the dozen they were...