A high roller who spent the night with a woman he had just met is found dead on the loading dock of the casino where he was staying. The investigation reveals that the victim won $10,000 in a pool game and was an assistant to a respected movie producer.

Coming straight from the perspectives of five people: Donna, Rebecca, Jack, Lou and Ray. All with one thing in common. They’re all dead. Brass and Catherine get to handle the case of Donna, who’s a cop from San Francisco, moonlighting as a bodyguard. Warrick and Greg work the case of Rebecca, who’s a former supermodel who died while hiking with her new husband Gavin. Nick and Sofia handle the case of Jack, a returning veteran from Iraq, who was killed in front of his wife and baby daughter who he just met for the first time. Grissom and Sara take the case of Lou and Ray whose bodies were found in Lou’s garage.

Grissom returns from his sabbatical; Keppler is put into a compromising position when the bodies of a Trenton police officer and a hooker are found in a hotel room. The man who found them is a retired New Jersey cop and close friend to Keppler, who doesn't reveal their relationship.

Grissom and the team join forces with Jack Malone, an FBI Agent from New York to track a serial killer.

The crossover continues on Without A Trace S06E06 Where & Why (II).

Catherine comforts Warrick when he is accused of murdering a famous Vegas gangster and even he is uncertain of his guilt or innocence.

A cache of missing chips from a closed down casino turn up in Vegas and a string of murders follow, leading Langston to use deadly force for the first time in his career as a CSI.

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