When the class clown at the local high school is found murdered, the CSI team is called to investigate, while Nick and Sara respond to the crime scene of a decomposed body found in a bag.

The student, who is also the top jock on campus, is found shot in the back in the school bathroom. The CSI team quickly discovers that the victim was also the class bully, and Grissom is convinced that he is looking for a classmate who was finally pushed to end the abuse once and for all. The team uses sophisticated new equipment to track the scent the killer left behind.

Meanwhile, Sara and Nick investigate a case involving a severely decomposed body of an Army veteran found in a bag.