Raymond Harris has been stalking Mac across New York. Not only is he stalking Mac but he is armed with a large amount of weapons. Mac is back at the CSI crime lab on a normal day. Hunt (Peter Fonda) is sitting at Mac's desk. He says that he has a text message from Mac asking to meet at the lab. Mac tells him that he never sent him a message to meet. Right as he shares that information with Hunt, bullets begin to fly into his office from the window. The bullets had been fired from the empty building across from the lab.
While the shooter is able to escape, the CSI team finds that the shooter had left the weapon and a duffel bag. The evidence leads the CSI team to an apartment – the same apartment where they had arrested Harris on drug related charges 17 years ago. They storm the apartment and engage in a shoot out. The man who lived in the apartment was killed but this time it wasn't Harris.
The team uses spatter science to analyze the evidence. Mac then realizes that Hunt was the real reason behind Harris' rage. Hunt had stolen money from Harris on the night that Harris was busted for drugs. His girlfriend had been murdered by Hunt while he was in prison. Mac, Hunt and Harris have a standoff and one of them does not survive.