Why stop there? Go back to "One To Go". If Grissom hadn't left, they wouldn't have had to replace him and none of the Ray/Haskell stuff would have happened.
Go back one step further. If Sara hadn't left in "Goodbye and Good Luck" and then again in "The Happy Place", Grissom wouldn't have left to go after her and...well...you know...
Go back one step further. If Sara hadn't left in "Goodbye and Good Luck" and then again in "The Happy Place", Grissom wouldn't have left to go after her and...well...you know...