Watch tonight’s “CSI” and you too will understand why Jorja Fox - Sara Sidle - quit.

Murders, suicide, a drag and dump (whatever that is), woman with knife in back, pre-pubescent homicidal insanity…all within 44 minutes. You’d quit too. One wonders what kind of toll this takes on an intelligent sensitive actress like Fox - year after year of it. She told “EW” that she wanted to start a family, but starting families requires a certain frame of mind, and “optimism” has to be a basic minimum requirement - optimism about life, your life, and the life of your unborn children. How could Fox be optimistic in a role that almost certainly bled into her off-screen psyche? (And how could it not?) “I spent almost my entire life with ghosts,” she tells Grissom in her goodbye-and-good-luck note. Nice line, and given this role, accurate. Time to move on and more credit to Fox for having the courage to forsake a very good paycheck for doing so.

As “CSI’s” go, tonight is merely average - which isn’t to say it’s bad, just merely average by “CSI” standards which would be high by anyone else’s. The B, C and D stories almost don’t matter here: The inevitability of her departure is etched into every scene and line, so the end comes as no surprise whatsoever (and of course everyone’s known it’s been coming for months anyway so no surprise was expected.) Even the episode title tips off the ending: “Goodbye and Good Luck.” It’s dry with just a touch of hope. And of course Sara lives. Of course.

There’s a flashback case here - fans will remember it well from last season, in the episode where the girl genius, Hannah West - Juliette Goglia of “Joan of Arcadia” - lies to save her brother, Marlon (Douglas Smith). The deranged duo is back, and poor little smart girl Hannah is up to her old tricks, plus she crawls right back into Sara’s head and messes it all up again. There’s no reason to go into any more detail, but the case is probably an appropriate one to end with because it serves to not only remind Sidle of her many ghosts but also of the fact that you can’t really bury them - they just keep coming back to haunt you. I’ve got to say, this departure is hardly suffused with optimism or the aforementioned hope: Sidle goes off into the figurative sunset with the harsh neon glow of the Vegas strip reflecting off her achingly sober face. Will Sara find happiness? Will Jorja? One certainly hopes they both do.