Sara Sidle (Jorja Fox) joined the CSI team in the second episode of season 1. She was brought on as a CSI by Gil Grissom (William Petersen) to replace Holly Gribbs (Chandra West), a new CSI who was murdered while processing her first crime scene. Sara had a pre-existing relationship with Grissom, having met him while she audited his lecture in San Francisco.
Sara started off as a workaholic loner who received a frosty reception from the other members of the team particularly Catherine Willows (Marg Helgenberger) and Warrick Brown (Gary Dourdan), whom she was asked to investigate due to his gambling habits.
As the series progressed, it is revealed that Sara had a foster home background after her mother murdered her father following years of spousal abuse. This gave Sara empathy and passion with regard to any case that involved spousal abuse and/or foster children leading Grissom to say "If I was looking for someone to stay up for three days straight I would ask Sara."
Over time it became clear that Sara was attracted to Grissom; however, her early advances went unnoticed, which led to depression and eventually alcohol abuse. She was caught driving while intoxicated and decided to clean up her act. Grissom supported her when she was faced with dismissal due to her actions, and their relationship became romantic. After Sara retired from the team, Grissom soon followed and the couple married and moved to Paris, although Sara does return to the lab to work on a temporary basis.
"I was really into gold stars when I was a kid."
"No. Actually, you and I are going to be seeing a lot of each other. If you thought the DA wouldn't prosecute a 12-year-old for murder, you were wrong. He wants justice for Stacy and her family."