The team investigates mysterious and unusual deaths to determine who killed whom and why, and also solves other serious crimes (such as rape). The show frequently focuses on a single case in each episode, or an investigation branched off from the main case (for example, episode 305, 'Legal,' in which a homicide in a nightclub is solved by Wolfe and Calleigh, while Horatio and Delko crack a prostitution ring being run by the nightclub's owner), as opposed to the two-cases-per-episode storytelling of its sister shows, CSI: Crime Scene Investigation, and CSI: NY. Many of its characters have appeared on all three CSI related shows because of the two-part episodes.