Death-row prisoner Kyle Boone is a serial killer who Gibbs arrested ten years ago; he insists that he will disclose the location of the missing bodies of his murder victims to Gibbs alone, forcing the reluctant team leader to meet with him. When Abby and McGee locate the place where the victims had been murdered, the team, assisted by Agent Cassidy, finds that the latest four victims in Boone's scrapbook had been killed in the last three years, meaning Boone has an accomplice. When Agent Cassidy goes missing, the team are forced into a desperate race against time to prevent her from becoming victim number five of the copycat killer.