FORTUNATELY for the citizens of Miami, there are plenty of serial killers in their midst.

While that might not seem advantageous at first glance - especially for the victims of these killers - I will now explain why it is.

If there weren't so many serial killers in the area, Dexter Morgan would have no one to kill except ordinary people. But because Dexter, who also happens to be a serial killer, targets only other serial killers, he apparently has plenty of victims of his own available on whom to prey.

On the new Showtime series "Dexter" - based on a character created by novelist Jeff Lindsay - Dexter's predilection for killing only other killers is seen as a boon to the community.

The community isn't aware of Dexter's "heroics," however, since he is so calm, cool and collected that he never gets caught.

He also happens to be employed by the Miami Police Department as a forensics expert specializing in blood spatter. This serial killer knows his way around a crime scene, which is a great help when it comes to cleaning up after his own crimes.

If you're confused, don't worry. Confusion is the inevitable by-product of a show that presents a serial killer as a hero.

Though he is outwardly likable, this particular "hero" happens to be as cruel in his own way as the killers he marks for death - which is one reason why the premise of this series is so bothersome.

Another reason is Dexter himself, who, as narrator, comes across as incredibly well-adjusted for a serial killer with a compulsion for systematically stalking and then butchering and dismembering his human prey.

He's a psychopath who acknowledges his emotional defi- cits freely - which makes it easy to sympathize with him, wrong as that might be.

Understandably, given its subject matter, "Dexter" is a gory show, but no more bloody than a typical episode of "CSI" or "Law & Order."

Like those shows, "Dexter" is a proficiently produced crime drama. Its best feature is its star, Michael C. Hall (formerly of "Six Feet Under"), who applies just the right touch to playing the nice, polite serial killer who lives next door.

"Dexter"