* House (8/7c Fox)
No, House and his gang haven't followed their last patient into that black hole she was hallucinating, but it has been a month since we've heard from them. So what's new? Cameron (Jennifer Morrison) is back, for one thing. And she and everyone else will have plenty of time to catch up because the hospital has been put on lockdown because of a missing infant, and everyone must stay where they are. David Straithairn guest stars as a crotchety terminal patient who must pass the lockdown time with House, and Hugh Laurie makes his directorial debut.
* Life Unexpected (8/7c The CW)
This drama about a foster teenager reconnecting with her birth parents wraps up its rookie season. As Cate prepares to marry Ryan, she attempts to sort out her feelings for both him and Baze, a man who has become an almost constant presence in her life ever since he reentered the picture with Lux. Meanwhile, Lux discloses some big news that could be life-changing for everyone around her.
* 24 (9/8c Fox)
For eight seasons now, fans have been rooting for Jack Bauer, super secret agent in the war against terror, even if we weren't always entirely sure we approved of his methods. But equally important to the series' success has been having somebody to draw our ire - and not just the obvious terrorist enemies. Returning tonight to the show for the stretch run is former president Logan (Gregory Itzin), the man whose picture ought to appear beneath the dictionary definition for "smarmy."
* The Big Bang Theory (9:31/8:31c CBS)
Since Sheldon loves superheroes and they usually have nemeses that never go away, it only seems fitting that Sheldon would have one, too. Wil Wheaton returns to battle Sheldon once again, and this time they face off in the bowling alley - though it's difficult to imagine Sheldon even picking up a ball, let alone playing. Also engaged in battle - but with words - are Penny and Leonard, whose argument threatens their relationship.
* Castle (10:02/9:02 ABC)
The late-night talk-show wars may have settled down, but it's still deadly terrain for talk-show hosts in Richard Castle's world. Tom Bergeron puts his gift of gab to good use playing Bobby Mann, a renowned host with a target on his back. He forewarns Castle of his pending death, but when Mann's prediction comes true Beckett isn't convinced of foul play. It then falls to Castle to change her mind. Meanwhile, a sexy celeb (Kelly Carlson) cozies up to Castle.