A mutilated female body is discovered tied to the undercarriage of a bus carrying prisoners from a women's correctional facility after a severed arm flies out from beneath the vehicle and strikes a car. Catherine leads the investigation and at first believes the woman was escaping, but the evidence increasingly points to murder. Back in town, Warrick probes the death of a gambler who was stabbed multiple times in his brother's kitchen.

Warrick, Catherine, and Nick try to determine the cause of a house fire that kills a teenage girl. The fire is in the same neighborhood as a similar arson fire. Grissom and Sara investigate a man found dead with letter tiles in his stomach. The man was a competitor in a word game tournament.