The flip side of television's love affair with bodily perfection is its increasing obsession with severed heads, putrefying organs, and the gnarly tangle of bones, nerves, and veins beneath the youthful flesh that often persuades us to turn on our televisions in the first place.

T.S. Eliot's characterization of the Jacobean playwright John Webster ("Webster was much possessed by death / And saw the skull beneath the skin / And breastless creatures underground / Leaned backward with a lipless grin") applies equally well to such hugely popular forensics shows as "CSI," "Bones," and "Numb3rs," or to the kinky plastic surgery saga "Nip/Tuck." Even comparatively wholesome programs like the hospital dramas "House" and "Grey's Anatomy" provide plenty of gruesome dissections for viewers to contemplate in high-definition close-up.

Now, upping the ante considerably comes "Dexter," which makes its premiere Sunday night on Showtime. Its hero, Dexter Morgan, brilliantly portrayed by Michael C. Hall ("Six Feet Under"), is a "blood spatter expert" working for the Miami police department who also happens to be a serial killer. The opening shot is of a full moon reflected in a puddle of water. Appropriately, it looks like an old, round skull out of the graveyard scene in "Hamlet."

A series that asks us to sympathize with, or at least tolerate, a serial-killer hero needs a good explanation for his behavior, and "Dexter" certainly has one. Through a succession of crucially convincing flashbacks we learn that Dexter was a foster child raised, along with his foster sister Debra (Jennifer Carpenter), who also works for the police, by Harry Morgan (James Remar), a legendary old-school Miami cop. Morgan realizes early on that his foster son is an instinctive killer consumed by blood lust.

Further flashbacks depict Dexter as a sweaty, increasingly feral adolescent, his savagery burgeoning even as he bows to the authority of his father, whom he holds in awe. "What happened to you changed something inside you," Morgan explains to his son, referring to some forgotten or possibly mythical incident in Dexter's life before he was given a home. "It got inside you too early. I'm afraid your urge to kill is only going to get stronger."

Having delivered this painful diagnosis, Morgan, who's seen a few serial killers in his time, decides to "fix" the problem the only way he can imagine. He teaches Dexter to channel his urges by becoming a "moral" murderer who will kill only the deadliest predators — serial killers who have evaded the law. (80% of Miami's murders, we are told, go unsolved.) He shows him how to do it and how to cover his tracks. As the grown-up Dexter sums it up, "I'm a very neat monster," and every crime he commits is done in accordance with what he reverently calls the "Code of Harry."

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