* DEXTER. 9 p.m. Sunday, Showtime.

* HOMELAND. 10 p.m. Sunday, Showtime.

ON THE SHOWTIME spectrum of personality disorders, Carrie Mathison, the CIA officer portrayed by Claire Danes in the network's new drama, "Homeland," barely registers.

Yes, those are some scary-sounding pills she's taking for a long-time mood problem she's neglected to mention to her security-conscious bosses. And, OK, it may be paranoia, not patriotism, that's led her to turn the home of a returning war hero into the set of her own private production of "Big Brother."

But this is Showtime, a refuge for pill-popping nurses, pot-pushing soccer moms and sympathetic serial killers - more about "Dexter" after the break - and on Showtime, Carrie's about as normal as they come.

So, too, is Marine Sgt. Nicholas Brody (Damian Lewis), who's picked up a few not-inexplicable quirks in eight years as a prisoner of war in Afghanistan.

Miraculously returned home after a rescue scene patterned on the discovery of Saddam Hussein in his hole, Brody's hailed as a hero by everyone but Carrie.

She, haunted by 9/11 and by an Iraqi prisoner's assertion that a U.S. POW's been turned, is convinced al Qaeda kept Brody alive all those years to use him in another attack on U.S. soil.

And there you have the setup for a game of cat and mouse in which it may not be clear for a while who's Tom and who's Jerry.

That's a level of ambiguity executive producers Howard Gordon and Alex Gansa might not have gotten away with when they were writing for Kiefer Sutherland's Jack Bauer on "24," but it's part of what makes "Homeland," adapted from an Israeli series created by Gideon Raff, one of the season's most intriguing dramas.

Ambiguity, though, can begin to feel like a cheat. What should keep viewers coming back to "Homeland"? The performances. In her first regular TV gig since playing iconic adolescent Angela Chase in "My So-Called Life," Danes is frantic, a dervish who can't quite fathom what's up with the guy she watches at all hours.

Lewis, mesmerizing in NBC's too-short "Life" as a different sort of ex-prisoner, projects an at times eerie calm as the man who, in a reversal of a paranoid fantasy, seems to be controlling a CIA operative though her TV set.

Showtime being Showtime, you shouldn't expect Carrie's voyeurism to exclude the bedroom, where Brody's reacquainting himself with his wife ("V's" Morena Baccarin), who wasn't the only woman to show up topless in the three episodes I saw.

Mandy Patinkin so far seems determined to keep his clothes on. (But then who can predict what Patinkin will do next?) As Carrie's mentor, Saul, he's a reminder that the lines Carrie's crossing really do exist and that not everyone at the CIA stays up all night watching suspected terrorists have sex.

Constitutional issues aside, that might be better than the way Dexter Morgan spends his evenings. As Michael C. Hall returns Sunday in "Dexter" for a sixth season as a serial killer with a code of conduct - and more lives than a cat - he's facing a new horror: his 20th high school reunion.

Mos Def, Colin Hanks and Edward James Olmos play characters with a religious bent in a season that doesn't yet feel as compelling as the one dominated by John Lithgow but allows Dexter to remain the way his fans most want him - alive and killing.