As Halloween descends on Sin City, the CSIs investigate when a creepy mannequin prop inside a popular haunted house turns out to be a real dead body. Also, Catherine enlists the help of Folsom to search for her friend who disappeared.

When three masked assailants invade a home and murder an entire family, including a pregnant woman, the CSIs are called to the scene to investigate. Catherine leads the team through the emotional case, which intensifies her own longing to reconnect with her estranged daughter, Lindsey.