KILLER SERIAL.

Most vigilante dramas plant their outrages up front--the murder of the architect's wife in "Death Wish," for instance--to enlist our approval of the ensuing slaughter of punks and loiterers. Showtime's "Dexter" skips all that, daring us to turn away. The pilot opens on a bleached-out Miami Beach evening, with Dexter Morgan (Michael C. Hall) cruising around and telling us, in zombielike tones, that he loves the city and its Cuban food, "but I'm hungry for something different now." Chinese? Apparently not. Dexter abducts a choirmaster and forces the man to confront the exhumed bodies of his youthful victims: "Look, or I'll cut your eyelids right off your face." Then he strips the man, binds him to a table, and revs his drill. Cue ungodly screams.

By day, a blood-spatter analyst for the Miami police, a master of reconstructing crimes from drips and spray, Dexter moonlights as a serial killer, preying on murderers who have escaped the cops' notice or a jury's reach, particularly those who killed or orphaned children. If you like rough justice, he's the best cop on the force--a one-man posse and hanging judge. (His pursuits don't always bear scrutiny, however. He uses his laptop to research an acquitted D.U.I. killer named Matt Chambers, and instantly pulls up clippings showing that the guy was involved in several other D.U.I.s--each time under a different name. So, let's see, you enter "Matt Chambers" and "aliases used" on Google . . .)

With rare exceptions, the detective genre demands that its savants pay for their acuity with a stunted personal life: hence Adrian Monk's O.C.D. and Columbo's imaginary wife. "Dexter," based on Jeff Lindsay's popular and rather purple novel "Darkly Dreaming Dexter," takes this deficit about as far as it can go. Our hero followed his foster father into police work, shares his doughnuts at the station, chimes in on the banter. But his true personality resembles his apartment: a sterile condo with the curtains drawn. Michael C. Hall, best known as David the repressed undertaker, on HBO's "Six Feet Under," is entirely convincing as a sociopath: his suet-lipped smile lingers a moment too long, and his movements and conversation are so robotic you half expect to see bionic relays glowing beneath his skin. At one point, he hands his foster sister and fellow-cop Deb (a coltish Jennifer Carpenter) an unwrapped gift.

Deb (mock enthusiasm): It's a cactus!, Dexter: You only have to water it three times a year., Deb: Gee, Dex, you didn't have to go out of your way., Dexter: I didn't. I was at the swap meet.,

The continuing story in this twelve-episode season concerns a psycho who kills hookers, drains their blood, and carves them into objets. Dexter admires his work the way Braque admired Picasso's, and uses his warped intuition to channel his rival's methods, telling Deb that the killer must have a refrigerated truck: "He wants a cold environment to slow the flow of blood." The Ice Truck Killer seems to be onto Dexter, too, and begins taunting him with clues. (The Serial-Killer Handbook requires that victims be accessorized with anagrams and rebuses.) Soon, predictably, the clues begin to point to Dexter himself.

It's hard to get worked up about Dexter's peril, because he keeps telling us that he expects and deserves to be caught, calling himself "a very neat monster" and "the little wooden boy." The sparks of dry humor he shoots off (naming his motorboat Slice of Life, for instance) may indicate that he's more human than he wants to admit, although in the uneven first few episodes it's hard to tell. We get a better sense of Dexter's icy relish of Grand Guignol from the show's credit sequence--lurid slow-mo closeups of him nicking himself shaving, then severing an orange and some fried-egg yolks--than from all his Vincent Price-ish voice-overs.

There's not much camaraderie at Dexter's station house, but the show tries to convince us that his colleagues are crusty yet decent folks who happen to be missing a part of themselves, just like Dexter (or those hookers). This campaign fails, partly as a consequence of Showtime's tendency to build shows around oversized characters like Dexter, who are ...