Rebecca Benefiel stepped into the tiny dark room on the first floor of the House of Maius Castricius. Mosquitoes whined. Huge moths flapped around her head. And – much higher on the ick meter—her flashlight revealed a desiccated corpse that looked as if it was struggling to rise from the floor. Nonetheless, she moved closer to the walls and searched for aberrations in the stucco. She soon found what she was looking for: a string of names and a cluster of numbers, part of the vibrant graffiti chitchat carried on by the citizens of Pompeii before Mount Vesuvius erupted in...