A popular prep school student , Olivia Prescot, was murdered on campus. The CSIs gathered evidence and uncovered a student making amateur porn, who said Olivia wanted to be a star.
Other evidence included the guts of an Emperor Scorpion, and "Martian" dust. The scorpion remains were from the shoe of a girl, Emmy Thomas, who had had a prank played on her. The "Martian" dust was actually Chilean desert soil from a science project being worked on by Emmy and another student, Allen Wilson.
The CSIs discovered that Allen had been helping Olivia study and had a crush on her. A cheat sheet on a water bottle also linked Allen to Olivia. Allen said that he had made the water bottle to help Olivia cheat, but didn't kill her. The only other person in contact with the soil was Emmy. Mac and Jo confronted her at the school and she confessed to killing Olivia because she was taking advantage of Allen.