After 12 years of crime-solving, Marg Helgenberger says farewell tonight, as her character of Catherine Willows bows out of CSI.

Will she be killed? Take another job? Retire?

We'll find out soon enough, but first we send Catherine off with a countdown of our favorite moments from her time on the CBS hit. Listed, in chronological order, there's been...

1. Catherine finding out that long-time family friend Sam Braun was really her father on "Inside the Box" (S03E23).
2. Catherine gaining sole custody of Lindsey after her ex-husband was murdered. "Lady Heather's Box" (S03E15).
3. Sam dying in her arms on "Built to Kill, part 2" (S07E02).
4. Catherine winking at Grissom as he walked out the door for the last time on "One to Go" (S09E10).
5. Catherine's relationship with Lou Vartann peaking with a steamy love scene on "Blood Moon" (S11E03).

Will we need to amend this list after tonight's episode? Perhaps. Did we miss any standout moment? You tell us!

Jim G. is a TV Fanatic Staff Writer. Follow him on Twitter.