Mac has been working at a lab in New York after leaving CSI. The lab he's at works to process recovered DNA from the found at the scene of the World Trade Center towers after the 9/11 attacks. In addition to his work at the lab he's also working hard leading the efforts for the 9/11 memorial. At the CSI offices, the team has had to redistribute the work. Much to her dismay, Jo has taken over Mac's role for the interim and Danny has been promoted to Sergeant. Each of the CSI team reflects on where they were when 9/11 happened while they solve the murder of a bouncer.