CSI is a curiosity. Long before the popular procedural drama became TV’s most-watched crime show, it bucked TV convention. CSI debuted on the same night and the same network as a slick, glossy remake of The Fugitive, one of TV’s most respected and fondly remembered classics. The conventional wisdom was that The Fugitive remake, starring a dashing Tim Daly, would be a hit, and CSI would be lucky if it played out the string for a season or two.

You know the rest. Like so many episodes of CSI, you know how this story ends long before you get there.

Popular doesn’t always mean loved, though. CSI has rarely, if ever, been considered for any major awards. It’s interesting, too, that though CSI does well in reruns, it does not do at all well on DVD. That suggests that CSI is the kind of show that people want to see at the end of a long, hard day, but they won’t go out of their way to keep it in their home video library.

CSI may leave a legacy that outlasts any award winner. Yes, it may be formulaic and obvious, but few networks are scrambling to rush out clones of award winners like The West Wing and The Sopranos. CSI’s influence, good or bad, will live on long after it’s gone.

That makes Jorja Fox’s departure from the show - tonight’s episode is her last - all the more curious.

Fox is not a particularly terrific actor. It’s not as if a movie career beckons, and there are unlikely to be any calls for new TV series for the next while - or as long as the writers’ strike lasts. Her character, crime-scene investigator Sarah Sidle, was something of a gift. In a show not noted for its breakout characters, Sidle provided one of CSI’s few interesting story arcs in recent seasons, as she struck up a tentative relationship with her supervisor and mentor, lab boss Gil Grissom - played with genuine chops by Chicago stage actor William Petersen, who turned the movie world on its ear in the ’80s in a couple of crime thrillers, Michael Mann’s Manhunter, an early precursor of CSI, and William Friedkin’s nervy chase thriller To Live and Die in L.A.

In tonight’s farewell episode, the appropriately titled Goodbye & Good Luck, Sidle encounters a spectre from her past - an encounter that leaves her shaken and questioning her future on the job. You already know how it ends, but that’s no different from any other CSI episode. Sarah Sidle always gets her man. It’s just that, this time, she walks away at the end. (8p.m., CTV; 9p.m., CBS)

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