The last episode of William Petersen as Gil Grissom on "CSI: Crime Scene Investigation" will be aired on Thursday, January 15. In "One to Go", Grissom will officially leave the unit and the show will welcome Laurence Fishburne's Dr. Raymond Langston as its regular.
As seen on the preview of this last episode of Grissom, there will be a few flashbacks of his scenes starting from the year 2000. The crime drama series aired its pilot on October 6 that year and Grissom had a scene with novice agent Holly Gribbs (Chandra West). It was in the episode that Grissom is known to have an eye for insects.
Peterson's character will stun his co-workers with an announcement that his time as a CSI has come to an end after working with Dr. Raymond Langston on the "Dick & Jane" murders, aired December 11. Before leaving the team for good though, he offers Langston a permanent position on the CSI team.