TONIGHT'S MUST-SEES

"Back to You," 7:30 p.m., Fox. In the blur of a strike-shattered season, one of the best situation comedies has been ignored. Now it's back, with five new episodes. In charge is TV's best comedy director, James Burrows ("Cheers," "Friends," "Will & Grace"). He has a terrific cast, led by Kelsey Grammer and Patricia Heaton. Tonight, a surprise party brings trouble: People might learn those two were lovers.

"Illicit: The Dark Trade," 8 p.m., PBS. As international trade became easier, this powerful documentary says, people found new ways to sell fake goods. That web of bribes has set up larger evils — guns, drugs and human slavery. In one chilling section, we meet a man who made millions by selling fake pills on the Internet.

OF NOTE

Presidential debate, 7 p.m., ABC. ABC hosts a Democratic debate between Sens. Hillary Clinton and Barack Obama.

"Til Death," 7 p.m., Fox. Previously, we met Kenny (J.B. Smoove), Eddie's new pal. Eddie hasn't had many black friends; he's torn when Kenny talks about facing a racial slight.

"American Idol," 8 p.m., Fox. The field is cut to six.

"Law & Order: Criminal Intent," 8 p.m., NBC. In a rerun of the well-made season-opener, a new murder brings a fresh look at the killing of Eames' husband eight years ago.

"Men in Trees," 9 p.m., ABC. Marin finally meets Julia (Kelli Williams), with whom Jack was shipwrecked.