A helicopter flies over Mesopotamia, its black metal shell blurred against waves of infernal heat. It lands at the foot of a pyramid and releases four passengers sealed up in combat gear. As they approach an ancient passageway, one stops, glares at the sky through obsidian goggles, and gives a middle finger to sun. Descending into the cool stone shadows, they remove their headgear and bear their fangs – vampires!

They are led by Danica Talos (Parker Posey), former Sundance goddess turned implacable goth seductress, and their mission is to rouse a great evil from the deep. A funnel opens in the sand, a spiked claw rises from below, “the patriarch of hominus nocturna” begins to stir … Dracula! He resembles a Hungarian porn star and you may call him Drake (Dominic Purcell).

Meanwhile, on the mean streets of Vancouver, the Daywalker clamps his jaw and swirls his leather cape. He is the legendary vampire-killer Blade (Wesley Snipes), a human-nosferatu hybrid with a penchant for Eastern metaphysics and trunkload of daylight grenades. Vampires fall in his monosyllabic wake, dissolving in a shower of orange sparks. They are no match for his sword, his boomerang, his stupendous firearms. When he chases them down in the Blademobile, they succumb before his righteous U.V. headlights.

Blade leaps on the last of his foes and impales him to the pavement. Take that, bloodsucking fiend! But it turns out this was a human; Blade has been tricked. From a nearby rooftop, Danica’s unholy manicure grips a DV camera, recording his grave blunder. Once the authorities are given the tape, they descend on the weapons lab/meditation loft of Blade and his human associate Whistler (Kris Kristofferson).

No sooner is Blade taken into captivity, though, than he’s sprung by members of the Nightstalkers, an upstart alliance of antivamp hotties. Abigail (Jessica Biel) is Whistler’s daughter, a bow-and-arrow expert, and totally bodacious. Also cool is Hannibal King (Ryan Reynolds), a former vampire successfully cured into a gun-toting smart aleck with rock-hard man boobs. Less so the blind scientist Sommerfield (Natasha Lyonne), who toils away at Nightstalker HQ on the fang busting “day star virus” while her daughter sits around waiting to be menaced.

These are the combatants of “Blade: Trinity,” which opens tonight at midnight, the third installment in what until now has been the sharpest of the Marvel comic adaptations. The “Spiderman” movies have heart; the “Blade” movies prefer to encase the hearts of mutant vampires in bone then stab at them upwards through the stomach. The “X-Men” franchise is informed by a corny subtextual plea for tolerance; the “Blade” franchise incorporates bold themes of class and race into its blockbuster ass-kickery.

A descendent of blaxploitation forefathers, Blade is a working-class superhero who sticks it to the (inhu)man. In the first film, Blade takes on a clutch of penthouse-dwelling uber-yuppies. They’re a splinter faction of the vampire elite, a shadowy multinational organization that plots its schemes in an ominous boardroom. In the sequel, he aligns himself with a troupe of multi-culti bloodsuckers, but is double-crossed by the vampire royalty, who dwell in a palatial corporate complex.

This comic-book populism is richly complicated by Blade’s status as a hybrid, a half-breed, a mixed-blood manpire. Rather than dilute his strength, this “impurity” lends to his powers. Blade the Daywalker can “pass” in the world of the living. Between the hapless humans and the ravenous, amoral vampires, he occupies the marginal middle, torn between opposing worlds, cultures, desires.

It’s not hard to see in Blade a semi-intelligible symbol for the blending of racial identities in America, to sense in the movies’ terror and mayhem an expression of cultural and psychological anxieties. But “Blade: Trinity” has not only given up on these suggestive subtexts; it has, far more grievously, abandoned the style, skill, and wicked humor of its predecessors as well.

Despite the brief but memorable appearance of a vampire Pomeranian, there’s nothing in “Blade:Trinity” as clever as the blood-cocaine from “Blade 2,” or the famous blood-sprinklers that doused a nightclub full of vampire hipsters in the original “Blade.” Those were presumably the inventions of David Goyer, writer of all three films, who’s been allowed to direct the latest.

This was a mistake. His writing’s gone lazy, and his direction is a sloppy grunge. The geometric combat of the earlier films has been replaced by a tyro’s technique: Place the camera close to the action and shake out an unintelligible blur. There’s no elegance of action, no giddy kinetic fun (like the hilariously pointless warehouse fight in “B2”), just aggressively boring business. Even the explosions are lackluster.

Drake is a big problem. There’s been no lamer villain in a movie this year. It’s bad enough when he bumbles through the street in a tunic, snatching babies like some absurd silent-movie meanie. As for his climactic incarnation as an armor-plated demon-bunny, no amount of CGI fang work can compensate for the shoddy rubber suit.

Ms. Posey, however, looks amazing. Decked out in plastic teeth, slutty heels, and an avant-whatever hairdo, she bites into the neck of her every scene and chews it to the bone. Maybe she’ll infect the franchise with her curse, and bring it snarling back to life.