In Room 217 of the Lakes Region Traumatic Brain Injury Clinic, something has awakened. Something evil. Brady Hartsfield, perpetrator of the Mercedes Massacre, where eight people were killed and many more were badly injured, has been in the clinic for five years, in a vegetative state. According to his doctors, anything approaching a complete recovery is unlikely. But behind the drool and stare, Brady is awake, and in possession of deadly new powers that allow him to wreak unimaginable havoc without ever leaving his hospital room. Retired police detective Bill Hodges, the unlikely hero of Mr. Mercedes and Finders Keepers, now runs an investigation agency with his partner, Holly Gibney -- the woman who delivered the blow to Hartsfield's head that put him on the brain injury ward. When Bill and Holly are called to a suicide scene with ties to the Mercedes Massacre, they find themselves pulled into a case that will put their lives at risk, as well as those of Bill's heroic young friend Jerome Robinson and his teenage sister, Barbara. Brady Hartsfield is back, and planning revenge not just on Hodges and his friends, but on an entire city.