They seem too good to be true at first, the two leads of Showtime's "Homeland," the best new show of the fall season. One is Carrie Mathison (Claire Danes), a tough, smart, dedicated CIA agent who can only be held back by her by-the-book superiors. The other is Sgt. Nicholas Brody (Damian Lewis), a Marine sniper who went missing in Iraq 8 years ago and was long presumed dead, only to be discovered alive and (relatively) well during a special forces raid on his captors' base.

The two could be poster girl and boy for the War on Terror, but almost immediately "Homeland" (it debuts Sunday night at 10) begins showing cracks in the facade.

We see quickly that Carrie may be more damaged than your average professional who just cares too damn much - that this may be a case where the by-the-book superiors know what they're doing when they try to rein her in.

Carrie's so twitchy and has so many skeletons in her closet that you can't blame mentor Saul (Mandy Patinkin) for being skeptical when she presents an alternate theory about Sgt. Brody: that he was kept alive for years - when any useful intelligence he could have provided would have expired within days - because he was turned by his captors and is now a terrorist with an All-American face and backstory. But because we get to watch Brody have awkward, at times unsettling, reunions with his wife (Morena Baccarin) and kids - reunions that Carrie herself is watching after setting up illegal surveillance of the Brody home - we can see some of the danger signs she does.

There are multiple possibilities with this set-up: that Carrie is mentally ill or just intense, that Brody was turned or is just slow to re-adjust, and various combinations of those four. (It could be, for instance, that Carrie is sane but also wrong about Brody.) And among the many smart things that "Homeland" producers Howard Gordon and Alex Gansa - a pair of "24" alums adapting an Israeli series - do is make it clear that any of those combinations could be equally compelling.

I'll confess that I mainly came to this series looking forward to watching Lewis, who's been one of my favorite actors since his leading man turn as the decent but never dull hero of HBO's "Band of Brothers." His work on NBC's short-lived "Life" - another role where he played a man of action struggling to return to society after a long captivity - is my current gold standard for the kind of performance you can do on a crime procedural if allowed. And Lewis is, unsurprisingly, terrific, conveying so much through stillness and silence (and, as always, disappearing seamlessly into the American accent) and letting so many moments seem ambiguous but not annoyingly so.

But the main attraction here is Claire Danes. In an impressive career that began with "My So-Called Life" and recently saw her winning every award short of the Nobel for playing Temple Grandin in the HBO movie of the same name, this is the best she's ever been, by a convincing margin. She's a bit too young for the role as written - Carrie's obsession is driven by her frustration over failing to predict 9/11, when she'd have been 22 at the time in the real world - but she's so good that it doesn't matter. As with Lewis, it's an extremely physical performance, one conducted frequently in silence (she spends large chunks of the episodes I've seen simply watching the Brody family from the comfort of her living room couch), but where she's constantly in touch with her surroundings and conveying every important piece of information through body language and expression. (There's a great sequence late in the pilot where she's trying to get dressed for a night out, and the mere act of her trying to choose the right top takes on as much weight as the conversation with Saul that led to it.)

What's most interesting about the performance and the character is that no matter what scenario is ultimately the right one for Carrie - right or wrong, sane or crazy - she is a complete and utter wreck in both her personal and professional lives (and who has a habit of mixing up the two). She will do anything, say anything, hurt anyone to get what she needs, all while completely neglecting her own physical and emotional well-being.(*)



(*) Danes, like most actresses, is extremely thin, but here it's turned into a sad running gag in which a colleague keeps trying to get her to eat, only to be horrified by the scarcity and rancidness of what's in her fridge.

Cable dramas have a rich tradition of male anti-heroes like this, and Showtime has somewhat cornered the market on "comedies" with dysfunctional female leads. But hour-long dramas built around this kind of female character are more rare (or they ultimately devolve into formula, like TNT's "Saving Grace"). Gordon and Gansa make no attempt to soften Carrie any more than they did Jack Bauer - though "24" as a whole was a show with much less nuance, moral or otherwise, where this is tonally much more like a paranoid '70s thriller (or Showtime's short-lived "Sleeper Cell") - and just trust that Danes will be so compelling that viewers won't care if they like her.

Along the way, "Homeland" functions terrifically as both a thriller and a commentary on our post-post-9/11 world, where the War on Terror and the concept of being constantly under surveillance are both facts of life. And where dramas like these often stumble with the domestic scenes, "Homeland" turns Brody's reacquaintance with his family - Baccarin, who was the primary, and at times only, reason to watch "V," is very strong as the confused, tentative Mrs. Brody (as is Patinkin as Carrie's most trusted confidante) - into important, interesting territory. Every bit of small talk he has with the kids, every uncomfortable romantic/sexual encounter he has with his wife provides clues to both us and Carrie about where his mental state is at.

The "Homeland" pilot has been available online for a few weeks now (and because of that, discussion of its contents are fair game here; if you won't see it til Sunday, don't read those), and I've heard both critics and regular viewers express skepticism that this show could be more than a one-season wonder. (Gordon and Gansa have said they have plans for a second season already, but that's what producers in this situation always say, whether they have a plan or not.) My thinking is this: I've seen three episodes that are great and that suggest a clear and obvious shape to this first season. If Gordon and Gansa can't come up with an interesting way to follow this initial story - or even if the first season deliberately stretches that story out, "The Killing"-style - then I'll worry about that then. Right now, what I see in front of me is so clearly fascinating that, like Carrie Mathison, I'm going to dive into the deep end and worry about consequences much, much later.

Alan Sepinwall may be reached at sepinwall@hitfix.com