As the lead in the new Showtime series Dexter, Michael C. Hall has devoted many hours trying to understand his character, Dexter Morgan, a self-acknowledged sociopath who by day works as a forensic pathologist and by night sets out to vivisect and eventually kill those who have it coming.

"He claims to be without certain fundamental human traits," Hall said recently during a shooting break on set. "He imagines himself as faking every human interaction. And yet there's something about him within the context of this world that's as human as anyone else."

A daring, macabre take on the traditional crime show, the series is Showtime's latest effort to find a breakout hit that might help close the subscriber gap with HBO. The past few years, Showtime's original series -Sleeper Cell, Weeds, Huff and Brotherhood - have generated critical praise but have failed to produce substantial ratings. Dexter producers deny that they are under any pressure to broaden the show's appeal and say they believe that the series remains in the traditional Showtime mode - it won't be for everyone.

New episodes are shown at 10 p.m. Sundays and repeated several times during the week. The second episode will be repeated at 11 p.m. today.

The series, set in Miami, is based on Jeff Lindsay's 2004 novel Darkly Dreaming Dexter, about a boy with a past so harrowing that he can't remember it, but which has left its psychological mark. Harry, his adoptive father, is a police officer who teaches Dexter to accept and use his murderous impulses for the public good.

As the grown-up Dexter pursues his gruesome "projects" - always following the "code of Harry" and slaying only those who have escaped official justice - another serial killer with a similar style challenges the police unit where Dexter works as a blood-spatter expert. The storyline unfolds over the season.

Producers knew that such a dark show couldn't last unless it were lightened up with humor. Writers found it in Dexter's predicament. Caring about other people as much as lawn furniture, he has had to teach himself to be charming to get along in the world. He has read profiles of serial killers and skillfully avoids displaying those characteristics. But now and then, such as when he tries to develop a relationship with a woman, he can't help but make comic mistakes.

"He's obviously a very cunning and capable guy, but in certain instances there's an innocence about him that is potentially funny, potentially endearing. I like the guy," Hall said. "Would that we all took such responsibility for our shadow sides," he said with a short laugh.

Perhaps the largest surprise in Dexter is that viewers are intended to relate - hopefully in a metaphorical kind of way. For one, there are the father issues. "He wonders, 'Am I just some sort of aggregate of my father's idea of who I should be?' Which I think is something many men deal with."

And then, there is the universal struggle for authenticity. "In a way, we all, to a certain extent, fake all human interactions," Hall said.

Though Hall said he strives for authenticity in his personal life, he was also at that very moment aware that he was speaking to a reporter and would not be the same if he were speaking to his buddy, his director or his mother. The key to playing Dexter, he said, is to realize that having cultivated so many personas, the killer is, in fact, an actor.

All that made Hall perfect for the part, according to Sara Colleton, an executive producer. "He's such a chameleon as an actor," she said. "I couldn't imagine it with anyone else."