The premise is simple enough: Vampires battle werewolves in a modern-day setting.

Yet the result is a disarmingly complicated story that grows weirder as it progresses. “Underworld” is neither scary nor particularly exciting — somewhat of a drawback for a monster movie — but there’s something absorbing about a tale so steeped in its own universe that the rest of the world barely seems to exist.

Adding to the flick’s dichotomous nature is its visual design, which is embarrassingly derivative. Maybe if filmgoers hadn’t been exposed to “The Matrix” or “Blade” franchises, this project might seem more revolutionary. Although the plot centers on bloodsuckers and shapeshifters, to the viewer it’s still just a bunch of supermodel types in form-fitting leather firing thousands of rounds of ammunition at each other while flipping, hurtling and posing.

On a side note: Wouldn’t this entire exercise be more interesting if no guns were used? One of the conceits about the undead is that they are innately powerful enough to not need modern weapons. It’s doubtful that giving Count Dracula an Uzi or Nosferatu a rocket-propelled grenade would dramatically improve their repute.

“Underworld” involves a vampiric S.W.A.T. team led by Selene (Kate Beckinsale). Her night gig is to slay Lycans, a group of werewolves with which her kind has been waging clandestine warfare for centuries.

When Selene helps save a human named Michael (Scott Speedman) that the Lycans are specifically targeting, she stumbles into a web concerning ancient bloodlines and unlikely alliances. Entangling matters is that she begins to feel something for Michael.

One other source that “Underworld” exploits is the works of William Shakespeare. (Think of the vamps as the Montagues and the wolfies as the Capulets.) But if you’re going to establish a Romeo and Juliet dynamic, Romeo better make an impression.

Unfortunately, Speedman seems to be personality-free. Thus the crux of the story — that a vampire could become smitten with a human — is a bit hard to swallow.

Kate Beckinsale portrays a vampire who hunts down werewolves because of an ongoing war between the species in the dark adventure Underworld.

Beckinsale isn’t exactly an actress one would describe as “bubbly,” but at least she’s a pro who has proven herself capable of carrying a lead role. In “Underworld” she desperately tries to generate a romantic spark with her co-star to no avail.

While Speedman may be dull, Irish actor Shane Brolly (as the vampire clan’s interim leader) is just plain awful. The gaunt hunk certainly looks the part, but he collapses when trying to summon the menacing intelligence that is necessary to portray such a scheming character.

On the flip side are Michael Sheen, as the scroungy leader of the Lycans, and Bill Nighy, as the hibernating vampire elder who is not pleased with being awakened a century too early. The veteran Nighy is particularly good, considering he functions while buried under an ever-evolving series of makeup and prosthetics.

Both U.K.-born actors’ ability at delivering venomous dialogue with a bit of a wink is an immense help to a film that is so relentlessly SERIOUS. It would be hard to name a release from this year that has less comic relief than “Underworld.”

The overall look of the production doesn’t cheer things up, either.

The murky, grainy effort might as well be shot in black and white because there’s barely a hint of color apparent. In some respects that’s a good thing, because it helps tone down how much red blood is spilled onscreen. But the desaturated textures also make it that much harder to tell who is who, as the characters all seem to be dressed in the same thing.

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This doesn’t help the frequent combat scenes. Sometimes they’re like watching a football game where both teams have on the same jerseys.

It’s obvious that former music video director Len Wiseman (who is engaged to Beckinsale) attempts to echo film noir with his visual choices. But it’s just too much, especially when the gloomy style crosses over into the human world. This is the type of movie where a bustling hospital corridor looks like it’s lit with a single lava lamp.

The best thing that can be said about “Underworld” is that it constantly keeps the audience guessing as to what is going to happen next. The strength of its narrative (by Wiseman and screenwriters Kevin Grevioux and Danny McBride) lies in how the characters and their motivations frequently change in terms of how the audience perceives them.

By the end, it’s obvious there aren’t any clear-cut “good guys and bad guys” in this peculiar picture. But one guesses that’s to be expected in a film about vampires and werewolves.

Kate Beckinsale, left, and Scott Speedman star in the dark supernatural adventure Underworld.