London, 1888. Meet Sarah. She’s fourteen, and her jawbone is dissolving. Sarah works in a match factory, dipping wooden sticks into white phosphorus—the chemical that makes matches strike. The phosphorus glows in the dark. The factory girls call themselves “the glow girls” because their skin literally shines at night. But the phosphorus is poison. It seeps through their skin, into their teeth, gums, and bones. Sarah’s jaw started hurting six months ago. A toothache. Then teeth fell out. Then her gums turned green. Now her jawbone is rotting from the inside. You can smell it across the room—the sweet, horrible smell of decaying bone. They call it “phossy jaw.” The bone keeps rotting. Her face will collapse. The only treatment is surgery without anesthesia—cutting away dead bone. Most girls die anyway. Sarah makes 4 shillings a week. Factory owners make thousands. This wasn’t hidden. Doctors documented phossy jaw in 1839. Factory owners knew. They didn’t care. White phosphorus was cheape...