"When she named off all 18 people and announced who was alive and who was dead, she hid the name of culprit X, and instead mixed in someone who wasn't on this island...! By doing that, even though the culprit was on the island, she was able to leave him out of the list of living or dead people! The person who was mixed in wasn't actually on the island, so he didn't count towards the total number of people on the island."