Grissom and Catherine investigate the murder of a despised comic who died onstage, apparently after drinking from a tainted bottle of water. The case grows more puzzling when a 15-year-old boy dies in a convenience store after drinking the same brand of water. Brass reopens a woman's accidental-death case after spotting the deceased's husband in a flashy new car with a trophy date on his arm.

A roller coaster runs off track leaving 6 people dead. The CSI team must uncover whether this was an accident, or foul play. Warrick and Catherine try to find the killer of a 13 year old girl.

Grissom is confronted with new evidence while on the stand of a murder trial of a restaurant owner. This development requires the reopening of the case and Eckley initiates an inquiry into Grissom and his team. The results of the inquiry lead to dramatic changes of the CSI team and the series.

The two forensic teams come back together under the leadership of Grissom and Catherine just in time to tackle three separate investigations: a murdered couple found in bed in a suspicious trailer explosion; a beautiful stripper discovered dead and dumped in the worst part of town; and two bodies found baked and decomposed after spending five days in the trunk of a car exposed to the hot Vegas sun, forcing the CSIs to ""wrap"" up the evidence and bring it back to the lab for further analysis.

The CSI team says goodbye to Catherine Willows as she makes a life-changing decision.

When eight bodies are found in what appears to be a meteor site in the middle of the desert, CSI Finlay recognizes one of the casualties, prompting her to revisit her past.