All serial killers commit murder to satisfy their grand fantasies, but the murderers featured in The Mark of a Killer, take it one step further, committing heinous acts that allow them to extend their fantasies and relive the excitement of their crimes again and again. With many keeping postmortem souvenirs and performing distinct rituals during each killing, their signature trademarks often prove to be their undoing. This series follows the trails of their obsession, and takes a deep dive into the killers' depraved psyches to reveal their darkest secrets as investigators close in to end the killer's reign of terror.