When a ghost hunter is killed in an abandoned slaughterhouse that was the site of multiple grisly murders in the past, the CSIs are called in to prove the killer was corporeal, and not the ghost of a deceased serial killer. The victim, Doug Lasky, was murdered in the exact way that serial killer Walter Simms killed his child victims, by hanging them on meat hooks and disemboweling them. Initial evidence seems to point to Doug's ghost hunting teammates, Owen and Carrie, as potential suspects, but that theory goes down the drain when Carrie is beaten to death at the slaughterhouse by another mysterious assailant. The CSIs dig into the old Simms murder cases and determine that he must have had an accomplice in his crimes, perhaps even another child he coerced into helping him. By cross-referencing the DNA from the recent crime scenes with the evidence from the Simms murders, they are able to track down their killer: Scott Tunnicliff, the property manager for the slaughterhouse. Tunnicliff was abducted by Simms as a child and forced to lure other kids to their deaths, and the psychological scars left by his experiences proved to be too much for him to handle.