After finding the decapitated body of a young man the CSI team believes that the killign was part of a ritual. Michael Wilson, the victim had residue on his body from a recent body wax and the wax was traced back to one of the hotels on the Las Vegas strip by the team. Wilson had been staying at that hotel and the CSI team search his room to find that he was in Las Vegas for a wedding that took place that day. Langston, Catherine and Nick head to the hotel chapel to speak to the wedding party and inform them of Wilson's death. However, upon arrival they find a room full of real-life vampires.
It turns out that Wilson and Julie, his fiancée wanted to get married at the annual vampire and werewolf convention, because they were practicing vampires and because they had met at the convention the year before. Vampires and werewolves are mortal enemies. The wolf hair that was found in Wilson's mouth has been traced back to Kurt Francis, a practicing werewolf. Additionally, DNA was found in Wilson's room on a yellow contact lens was tracked back to Francis. The CSI team searches Francis' truck and finds WIlson's blood and some digestive enzymes required for someone suffering from porphryia , "vampire's disease."
It turns out that Wilson was actually a werewolf and had belonged to Francis' werewolf pack. However, when he met Julie and fell in love with her, he changed to a vampire, for her, so they could be together. Francis confronted Wilson when he recognized him dressed as a vampire. He and another vampire, Thomas Stewart, decide to kill Wilson. Thomas was able to convince Julie that Wilson had ultimately betrayed her and she was actually the one to take the first deadly strike at Wilson.