| Season Number: | 4 |
| Bgcolour: |
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| Starring: | William Petersen Marg Helgenberger Gary Dourdan George Eads Jorja Fox Eric Szmanda Robert David Hall Paul Guilfoyle |
| Num Episodes: | 23 |
| Network: | CBS |
| Episode List: | List of CSI: Crime Scene Investigation episodes |
The fourth season of premiered on CBS on September 25, 2003, and ended May 20, 2004. The series stars William Petersen and Marg Helgenberger.
Nick accidentally leaks information to a news reporter ("Assume Nothing"), and Catherine tries to discover how a body ended up in a bathtub ("All for Our Country") during the fourth season of CSI. Supervised by Grissom and Willows, the Las Vegas CSIs are tasked with investigating the bizarre, the unlikely, and the unprecedented, including a disappearing gun ("Homebodies"), the death of a baby during a heatwave ("Feeling the Heat"), a case of raccoon versus big rig ("Fur and Loathing"), a car-bombing ("Grissom Versus the Volcano"), and the derailment of a roller-coaster ("Turn of the Screws"). Meanwhile, Catherine usurps a case from Nick and Sara ("After the Show"), the team have to re-investigate a rape-murder ("Invisible Evidence"), Grissom heads to Jackpot, Nevada ("Jackpot"), and team take part in a CSI relay, bringing together investigative teams from across America ("Dead Ringer").
See main article: List of CSI: Crime Scene Investigation characters.