Gil Grissom investigates a murder staged to look like a suicide, and his deputy Catherine Willows gathers evidence from a young girl who has been sexually abused. Meanwhile, Warrick Brown and Nick Stokes are competing to solve their 100th case to earn a promotion to CSI 3.
Gil Grissom takes over as head of the CSI unit when Brass is transferred to homicide in the aftermath of Holly Gribbs' shooting. With Gribbs in hospital, Grissom brings in Sara Sidle to help investigate the incident, while he and Nick look into the case of a man who killed himself mere hours after winning a fortune on a slot machine.
Grissom and Catherine investigate when a woman's severed leg is discovered in a lake. They suspect both the husband and boyfriend of the woman's murder. Meanwhile, Sara and Nick try to uncover the real cause of a student's death, and Warrick realises that he owes Judge Cohen - big time.
Sabrina takes a job as a sandman, and her aunts warn her that she shouldn't meddle in other people's dreams as it can influence events in real life.
But a little girl who witnessed her grandfather leap into a chasm begins to feel an overwhelming sorrow.