When a human skull and torso are found on top of a double-decker tour bus in Times Square, the CSI's must determine whether it was a practical joke or murder. Based on the bone structure, Dr. Hawkes determines the victim is a Caucasian male teenager who most likely died from a blow to the head. Stella gets a hit in AFIS from a fingerprint found on the skeleton that leads to a Port Authority Bus Terminal worker, who admits pulling the prank. A black coating of diesel exhaust on the bones containing high levels of Benzene, not EPA approved since 1994, proves the victim has been dead at least ten years. Mac follows bus exhaust to a nearby basement and recovers the rest of the victim's bones, and the victim's meager possessions, including a pocketknife, backpack, artwork, and a book copyrighted in 1984, narrowing the CSI's timeline from 1984 to 1994. At the lab, Aiden uses the skull to reconstruct "John Doe's" face in clay. The parents of a boy missing since 1987 reveal the knife and backpack belonged to their son, Aaron Moreland, but "John Doe" is not their son. Mac finds a "blank" piece of paper in the victim's pocket and utilizes multiple forensic tests to recover the faded print, revealing it's a 1990 pawn ticket for a watch. At the pawnshop, they learn the watch was recently purchased, but video surveillance catches the mystery buyer nonchalantly strum a guitar. The CSI's recover epithelials and match them in CODIS to the missing Aaron Moreland. Using "aging" software on a photo of Aaron, supplied by his parents, leads Mac and Stella to 34-year-old Aaron. Aaron confesses he was a clothing rack runner with the victim and would trade his possessions for money to buy drugs. When the victim took the pawn ticket for Aaron's watch and only gave him two dollars in return, Aaron snapped and hit him in the head with a pipe. Mac and Stella bury the still unknown victim in a pauper's grave.