CLINICIANSA word that will come to haunt Casualty Sister Rachel Young through the dark nights ahead.CLINICIANSA word she hears from a terrified patient, brought dying into her department after driving a stolen car straight into a brick wall. Still trying to escape from someone who has surgically mutilated his brain.CLINICIANSHe isn’t the first; he won’t be the last. People are disappearing in the darkness: the lost ones, with no shelter from the night. Those that are found again have hideous post-operative injuries.CLINICIANSFor centuries they have pursued their cold and merciless quest for knowledge, leaving death and mutilation in their wake. And tonight they have come for Rachel Young. for her, they have a special role …