On the trail of a cannibalistic killer, Luther is dogged at every step by ghosts from his past. Isolated and on edge, it takes every fibre of his being to keep it together. Could a cold case help to unlock a mystery that's tormenting him? Meanwhile, the serial killer is still on the loose. Benny's hacking skills have revealed a list of hundreds of potential victims but, with a rapidly escalating number of crime scenes, Luther must use all his ingenuity to work out where the murderer is headed next. Discovering it's all part of a macabre end game, Luther is forced to put himself and his new colleague Emma into the heart of danger to try to stop the killing.