The entire CSI team investigates a disappearance at a local university. A young woman vanished, seemingly off the face of the earth. Forensics leads them to possible suspects, and possible suspects all have probable motives, but nothing seems to pan out. This leads our team to discuss the "Chaos Theory." When combined, many seemingly-innocuous events may have a deadly outcome. And closure is not always within reach.

When the class clown at the local high school is found murdered, the CSI team is called to investigate 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.