The bodies of twin teenage boys, kidnapped five years earlier, are discovered. Booth and Brennan follow the trail of a notorious serial killer, known as the Grave Digger. His M.O. is to kidnap and bury his victims, then ask for a ransom. If the ransom isn’t followed, the victims are left to die. During the investigation, Brennan and a fellow colleague become the latest victims. They are forced to solve their own kidnapping from an underground grave.