Jokes proliferate in “Vampire Academy”—most of them groaners—but the biggest is reserved for the very end, when a coda sets the stage for a sequel. The chance of that happening is about as great as a follow-up to “Heaven’s Gate.” Not that Mark Waters’ adaptation of Richelle Mead’s young adult book—the first of a six-volume series that crosses “Twilight” with “Harry Potter”—is an expensive fiasco. From the look of it, it’s a pretty cheap one; but it’s a fiasco nonetheless.

One can glimpse what Waters was aiming for here—a combination of the dark high-school humor his brother Daniel, who shares script credit with Mead, brought to “Heathers” (and Mark himself did to “Mean Girls”) with the elements of a supernatural action-thriller. But he proves to be no match for the Joss Whedon of “Buffy” days in concocting such a mixture.

The heroine of the piece is Rose Hathaway (Zoey Deutch). She’s what’s categorized as a Dhampir, a half-breed who’s vampire on one side and human on the other. She’s the protector, best friend and occasional source of blood for Lissa Dragomir (Lucy Fry), a royal princess among the Moroi (good vampires), as distinguished from the ravenous Strigoi. As the story begins, after a year on the run they’re found by Dmitri Belikov (Danila Kozlovsky), an expert Guardian at St. Vladimir’s Academy for Moroi teens, from which the duo escaped but to which they’re now returned. The balance of the picture has to do with a plot against Lissa perpetrated by a mysterious villain, interrupted by halting romances between Rose and Dmitri on the one hand and Lissa and brooding bad-boy Christian Ozera (Dominic Sherwood) on the other.

Mead apparently invented an elaborate mythology for her tale—the preceding paragraph notes only its most rudimentary aspects—and the script tries to shoehorn in most of it. The result is that the picture features a mind-numbing amount of exposition, and keeps adding wrinkles to the basics whenever the plot runs into a dead end. Some of the Moroi, we learn, have magical powers, and can “compel” others to do their bidding. (That’s associated with an Eastern European background, including what appears to be a Russian Orthodox chapel where a priest regularly instructs the students about St. Vladimir who—it turns out—had the power to revivify the recently deceased, an ability others might share.) There’s also a sort of mind-meld operative between Rose and Lissa, which somehow allows the former to go into a trance and observe things from the princess’ perspective. Another twist involves a charm that induces raging passion, and toward the close a couple of giant dogs—rather chintzy CGI critters—suddenly appear with little explanation. By the sixty-minute mark most viewers who are unfamiliar with the book will simply have thrown up their hands in exasperation trying to figure out what’s going on, though they’ll probably have little difficulty identifying the villain long before the name is revealed; a glance at the cast list alone will suffice to point one in the right direction.

The performances are uniformly weak. Exuberant Deutch comes off like the star of a comedy series on Nickelodeon, which is where this movie would feel quite at home, while Fry flounders in a role utterly lacking in consistency and Sami Gayle, as her “mean girl” tormentor Mia, is so over-the-top that she’s unintentionally hilarious. The lead guys—Kozlovsky and Sherwood—are stiffs, and Gabriel Byrne stumbles around as an infirm friend of Lissa’s family. One casting oddity involves Claire Foy, who’s almost a dead ringer for Helena Bonham Carter as Ms. Karp, a strange teacher at the school. Her presence ratchets up the “Potter”-esque vibe considerably. Technically this is a very modest production, though the English location—standing in, not entirely convincingly, for Montana—is attractive and Tony Pierce-Robert’s wide-screen cinematography is nice.

Mead’s books have a substantial fan base, but so did the “Mortal Instruments” series, and that certainly didn’t bring droves into the theatres for “City of Bones.” A similar fate is likely to befall this toothless genre mash-up, which should finally put a stake into the heart of these teen vampire movies.