An exclusive mobile club located in the back of a truck was driven into the river injuring many of the guests, and killing three people. Among the victims was the daughter of a notorious union boss, Carmen Enzo. Mack first considered that the murders had been a warning towards Enzo, and told Enzo to stay away from the investigation.
The investigation shifted gears after the roommate of one of the victim's, Jessica Thomson, came forward and told the police that she had been invited to the party, but had given her invitation to her roommate because she had to work late. After questioning some of the survivors three other people in the truck had been sent exclusive handmade invitations to the club and had experienced harassment from an unknown stalker.
Jessica recognized her ex-fiancé from a sketch given to police as the man who had ordered the invitations inviting Jessica and the three others to the club. After discovering Jessica's ex's body with a matching invitation in his pocket the CSI concluded that one of the survivors was actually the killer. Secondary interviews led to the arrest of Neal Cooper. Neal was shot outside the police station by Carmen Enzo.