Dexter Dexter

9/8c Showtime
The Trinity Killer (played with chilling dastardliness by John Lithgow) is still at large, which is really getting under Dexter's skin. So the forensics whiz feels compelled to step up his personal involvement in investigating the case. On the home front, previously clueless Rita becomes privy to one of Dexter's secrets, and she wonders exactly how much more there is to her enigmatic husband and his mysterious ways. — Ray Stackhouse

Curb Your Enthusiasm
9 pm/ET HBO
The much-hyped Seinfeld-reunion story for the seventh season took a backseat the last two weeks, but that doesn't mean Larry's run-ins with Christian Slater, Rosie O'Donnell and Philip Baker Hall's Dr. Morrison haven't been hilarious. Moreover, Larry's self-serving empathetic streak while two-timing a pair of women in wheelchairs was a new low, even for him. Tonight Jerry Seinfeld is back to discuss plot devices for the special, but do you think Larry will mention his role for Cheryl? — Joe Friedrich

Desperate Housewives
9/8c ABC
So now we know that Nick Bolen is the married guy who has been having the affair with Julie Mayer. Where will it go from here? Who knows, but look for a lapse in judgment on Danny's part to cause trouble. Meanwhile, things are heating up between Bree and poor, lovesick Katherine (and that's in addition to an expected Susan-Katherine blowup). And speaking of looove, Bree is called out for her affair with Karl — by a motel maid. — Paul Droesch

Mad Men
10/9c AMC
A former client who makes dog food, and is trawling Madison Avenue for new representation, drops by Sterling Cooper. In the midst of a "public-relations crisis" that saw sales plummet, the company president tells Don and Roger that the firm with the best idea for inventing "a word for horse meat," which is what all puppy chow is made of, gets her business. Plus Betty takes the kids on a trip, and Joan (!) and Greg discuss their future. — Ray Stackhouse

Masterpiece Contemporary
9/8c PBS (check local listings)
A strong cast accents Endgame, about how British businessman Michael Young (Jonny Lee Miller), who represented Consolidated Goldfields, played a part in bringing an end to apartheid in South Africa. Miller's costars include William Hurt as academic Will Esterhuyse, who negotiated for the Afrikaner side; Chiwetel Ejiofor as Thabo Mbeki, who represented the ANC; and Clarke Peters as Nelson Mandela. — Jeff Gemmill