The episode opened with a couple exploring sacred burial grounds on Halloween, while filming something happens and one begins screaming while the other is thrashing on the ground.
Five-O was called in shortly thereafter when the room-mate to the couple identified the hand sticking out of the ground as Christian O’Connor. He and his girlfriend Kat Forrester were the two people murdered and buried in a shallow grave on sacred ground.
After Max figured out that Kat had a fingerprint on her glasses from a guy who’s been dead for over a week, the trail led to a mortuary funeral director and nurse who were providing bodies for harvesting tissue to sell on the black market.
The mortuary funeral director was found dead and when Five-O confronted the nurse he blew himself up igniting Formaldehyde, leaving the killer of the couple in question, but unsolvable.