As the team grieve for their fallen colleague ("For Warrick"), Grissom makes a life changing decision ("One to Go"), during the ninth season of CSI.

Also this season, Sara investigates the death of a woman attacked nine years ago ("The Happy Place"), new CSI Riley Adams joins the team ("Art Imitates Life"), and she and Nick witness a store robbery on Halloween ("Let it Bleed"), Grissom attends the trial of the Miniature Killer ("Woulda, Shoulda, Coulda"), and an infamous serial murderer brings Dr. Raymond Langston face-to-face with the CSI team ("19 Down").

As Catherine adjusts to life as the team's leader, she investigates the bizarre, the brutal, and the unlikely, including an S&M related murder ("Leave out all the Rest"), an arson-homicide ("The Grave Shift"), the murder of an FBI agent ("Disarmed & Dangerous"), death-by-toothpaste ("Deep Fried & Minty Fresh"), and a Mexican wrestling related death ("Mascara").

A writer and producer of episode 13 ("Deep Fried and Minty Fresh"), Sarah Goldfinger, was sued for defamation of character by California real estate agents Melinda and Scott Tamkin.

[1] William Petersen and Gary Dourdan both depart the main cast, and are replaced by Lauren Lee Smith and Laurence Fishburne.