TONIGHT'S MUST-SEE

"CSI: Crime Scene Investigation," 7 and 8 p.m., CBS. After almost nine seasons, William L. Peterson steps down from the show he helped turn into a huge ratings hit. First is a rerun of the episode in which Grissom (Peterson) was perplexed by murders linked to a serial killer. He attended a class taught by pathologist Raymond Langston (Laurence Fishburne). Then is a new episode. Grissom again needs Langston's help, then offers him a job.

"The Beast" debut, 8 p.m., A&E. Charles Barker (Patrick Swayze) is your standard tough-guy cop, Hollywood version. He's smart, angry, intense; he breaks the rules, the way film cops are supposed to. Now he has a quiet, young partner (Travis Fimmel), with fresh-from-training ethics. They work on a gun-smuggling case, while the kid learns. On paper, "The Beast" does all the right things. Still, A&E repeats the mistakes it made with "The Cleaner." This opener is relentlessly dark, both visually (with Chicago in the winter) and emotionally; there's a good-enough story, but it's a tough trip for viewers.

OF NOTE

"Ugly Betty," 7 p.m., ABC. Last week's episode ended with a jolt: Betty had ignored calls from her sister; when she got home, she learned their dad had had a heart attack. Tonight, the sisters argue and Betty feels the tug of work.

"Grey's Anatomy," 8 pm., ABC. Cristina awaits her first date with Owen (Kevin McKidd). Meanwhile, Derek's mom (Tyne Daly) finally meets Meredith; also, Mark tries to conceal his relationship with Lexie.

"The Office," 8 p.m., NBC. By now, Andy is the only one who doesn't know about the affair between his fiancee Angela and Dwight. That secret isn't safe with Michael.

"Treasure Quest" debut, 8 p.m., Discovery Channel. Armed with modern technology, Odyssey Marine Exploration has discovered sunken treasures from four centuries ago, Now this 11-week series follows its search for a ship with treasures that might now be worth a half-billion dollars. These are amiable guys with quick humor; still, it's not that interesting to see people probe for something in the murky depths.

"30 Rock," 8:31 p.m., NBC. Dr. Spaceman — pronounced Spa-CHEE-man — is being very selective about giving out flu shots.

"ER," 9:01 p.m., NBC. Neela has recurring dreams about her efforts to help a young girl with sickle-cell anemia. And at an interview for a promotion, she sees a surprise — the return of Elizabeth Corday (Alex Kingston), a former "ER" doctor and Mark Greene's widow.