On last week’s episode of “CSI”, in the crossover stunt featuring “Without a Trace**s Jack Malone, Sara Sidle was shown as visibly shaken at an especially unsettling crime scene, walking away as if she’d had enough. Her psychological unease and emotional exhaustion had been well established even before last season’s cliff-hanger that left her trapped under a car in the desert, as fans wondered all summer if TV’s top procedural was going to kill off one of its own. Thankfully, “CSI” (as usual) took the high road, and this story reaches its destination tonight.

Unless you’ve been in solitary the last few months, you know that tonight’s heavily promoted (and for once, worth the hype) episode marks Sara Sidle’s, and Jorja Fox’s, departure from the series. Without going into the specifics (which would be wrong), let me just say this is a terrific farewell: melancholy, creepy and, most important, providing a dignified exit for an important character who will always be welcomed back into the fold – and not just by her mentor-turned-lover Gil Grissom (William Petersen, who’s also excellent in this moody episode).

Jorja Fox has always made it clear in her portrayal of Sara that this crime-scene tech is unusually susceptible to taking cases personally, to letting them get under her skin. That’s certainly true in this episode, which resurrects a particularly troubling case from a previous season, involving a manipulative child genius (well and disturbingly played by Juliette Goglia) who knows just how to push Sara’s buttons.

“You look different than you used to be: angry and a little said,” scary little Hannah tells Sara in one of their encounters.

Smart girl. Poor Sara. Nicely done, “CSI.”