When Dr. Craig "Huff" Huffstodt gets a midlife wake-up call, it's a doozy.

In the middle of a session with a troubled gay youth, Huff - a successful psychiatrist and family man played by Emmy winner Hank Azaria - is horrified when the young man abruptly pulls out a handgun and kills himself right there in the office.

This shocking incident sends Huff reeling, and not just from the legal implications he has to deal with via best friend and attorney Russell Tupper (Oliver Platt). After all, things aren't exactly rosy at home either.

Oh, sure, his wife, Beth (Paget Brewster), adores him, and so does precocious teenage son Byrd (Anton Yelchin, the gifted young actor from Showtime's recent original movie "Jack"). Boosting the tension level on the home front is Izzy (Blythe Danner), his controlling mother, who has lived in the apartment above the garage ever since she learned that her husband (recurring guest star Robert Forster) had another family halfway around the world as a result of his military service in Vietnam.

Izzy loves Huff, too, but that only means she constantly engages poor Beth in a guilt-mongering battle of wills over what is best for him. As if that weren't enough for Beth, Huff also is being stalked by a psycho ex-patient (recurring guest star Lara Flynn Boyle) who feels psychically connected to him.

Oh, and in case you were wondering: "HUFF" - which debuts at 10 p.m. Sunday on Showtime, Channel 14 - is a comedy.

It's a very dark one, to be sure, a complex, challenging piece cut from the same cloth as HBO's "Six Feet Under," the hit cable series that Showtime Networks Entertainment President Bob Greenblatt helped develop in an earlier job.

In addition to a similar tone, both shows are populated by prickly, multi-dimensional characters who defy easy pigeonholing; story lines that deal with big issues of life, love, family and mortality; and superior casts obviously picked with great care.

Azaria, whose credits range from heavy historical dramas ("Uprising") to voice work on "The Simpsons," clearly relishes playing a man who is almost peerless at helping others yet cannot cope with his own crisis.

"Huff is very competent, but ... his crisis is affecting the way he handles things personally and professionally," Azaria says. "Like a lot of therapists I know, it's (a case of) 'Physician, heal thyself.'

"I majored in psychology in college, and the kids of the therapist were some of the most screwed-up people I've ever met in my life, which is a surprising thing. The greatest mystery to Huff is certainly himself."

Each episode tilts unpredictably between laugh-out-loud comedy and searing pathos, as in the scenes between Huff and his young brother, Teddy (Andy Comeau), a diagnosed schizophrenic currently living in a locked facility.

"What binds the seriousness and the humor is always honesty and reality," Azaria says. "Life tends to hand you a lot of horror, happiness, joy, misery and sadness. James L. Brooks (writer-director of 'Terms of Endearment') is someone who, in film, manages to do that. That's what we're shooting for."

Azaria also says he finds intriguing Huff's longtime friendship with Russell, whose recreational drug use borders dangerously on the self-destructive.

"Huff can see his best friend clearly is an addict," Azaria says of that relationship. "How do you handle that? You can't 'therapize' them if they don't want it. There are times when Huff wants to say more and doesn't. In life, sometimes you know how you could help someone but they don't want the help. What do you say? Can you stay friends with them?"

"Russell is a very, very good lawyer," Platt says of his character, "and like a lot of high-functioning professionals he is a victim of his own compulsive behavior. Professionals (like him) tend to lubricate their denial and think that they don't really have a problem."

Perhaps none of the cast members handles the quicksilver shifts in mood more deftly than Danner, reveling here in the best role she has had in years. With her grandson, Danner's Izzy is the embodiment of selfless love; with her daughter-in-law, she is a hypersensitive nag finding offense and disappointment in every act and syllable. It's a fascinating performance.

"I love that she is three-dimensional," the Tony-winning actress says. "She's not just a bitch on wheels running roughshod over everybody, although she does that sometimes. I love playing her irreverent, irrepressible (side). It's so refreshing, and sort of like being let out of drama jail."

It remains to be seen how Showtime's mainstream subscriber base will cotton to the show - "I know parts of it have upset a few people," Azaria acknowledges - but Showtime Greenblatt says the premium channel already has picked up "HUFF" for a second 13-episode season.

"We couldn't be happier about this show creatively," he says. "Bob Lowry (the show's creator and executive producer) has a very strong vision for 'HUFF,' and actors the caliber of Hank, Oliver and Blythe could simply see that in the writing.

"There still aren't a lot of networks for original voices to be heard, so we've made it known that that's the business we're in. Our job is to find these visionaries, nurture them and then get out of their way. The rest of it will take care of itself, because the strength is in the material."