Carolyn Keene’s teenage shamus, who debuted on the printed page in 1930, hasn’t been seen on the big screen since the late thirties, when Warner Brothers made a quartet of low-budget pictures featuring her. Apart from a short-lived TV series starring first Pamela Sue Martin and then Janet Louise Johnson in the late seventies (and an even shorter-lived mid-nineties syndicated series), Nancy Drew has remained in hibernation since then. And on the evidence of this attempt to resuscitate the character for today’s adolescent girls, she probably should have been kept in mothballs.

It’s hard to say whether any approach could have made “Nancy Drew” work for modern audiences. The earlier features, as might be expected of their time, were fairly true to the books, but the seventies series modernized her to excess, and the nineties effort depicted her older and on her own in the city, which merely conventionalized the character pretty much beyond recognition. Perhaps at this date a period effort would have been the most interesting choice, even if it might have seemed quaint. But what Tiffany Paulsen and Andrew Fleming offer is a hybrid that transports small-town Nancy—a throwback in her sensible clothes and penny loafers—to contemporary (though very benign) Los Angeles, going for a kind of Betty Thomas “Brady Bunch Movie” effect, though without the saving note of parody. This new “Nancy Drew” uncomfortably straddles the line between revival and send-up, coming across as something that might be suitable for Nickeloldeon, say, but is utterly out of place in theatres. The cable-TV feel is accentuated by the presence of Emma Roberts, a stalwart of the kids’ network, in the title role. Her affected, one-note turn will make it difficult for tween girls even to like the character, let alone identify with her.

Plot-wise, too, the story concocted by Paulsen and Fleming is an odd amalgam of the old-fashioned and the contemporary. On the one hand Nancy, who’s temporarily relocated from River Heights (where she’s the town’s premier crime-solver) to California when her lawyer dad Carson (Tate Donovan) takes a case there with high-powered attorney Dashiel Biedermeyer (Barry Bostwick), has to contend with the trauma of fitting in at a new high school. She’s ridiculed by mean girls Inga (Daniella Monet) and Trish (Kelly Vitz) and pursued by the former’s infatuated little brother Corky (Josh Flitter, the caddie from “The Greatest Game Ever Played,” who still looks like a lawn gnome). But it juggles this teeny bopper fluff, made even more dopey when Nancy’s home-town boyfriend Ned (Max Theriot) shows up for a visit to create a “romantic” triangle, with a really creaky mystery scenario that might have come out of the 1930s.

That concerns the old mansion Nancy’s arranged to rent while she and dad are in L.A.—the erstwhile home of Hollywood star Dehlia Draycott (Laura Ellen Harring), whose murder years before has never been solved. Nancy’s investigation of the crime, which she has to keep secret from her father, comes to involve the hoariest of plot devices—boxes with hidden compartments, secret tunnels, threatening messages (though now on cell phones or via text messaging), pursuit by car (or, now, SUV), and a sinister-seeming caretaker (Marshall Bell). And though one doesn’t want to reveal too much about the solution, some parents may find it wrongheaded, in a movie aimed at youngsters, that it involves not only an illegitimate birth (Nancy tracks down Dehlia’s out-of-wedlock daughter, played by Rachael Leigh Cook), but strained single motherhood (and even an episode involving a child being taken from her mother’s care by CPS).

“Nancy Drew” is thus an uneasy combination of high-school comedy and retro nostalgia that succeeds as neither. Roberts’s stilted lead turn is matched by the rest of the cast, who all seem to be acting in italics—an approach hammered across by Fleming’s heavy-handed direction. The physical production is okay, though Alexander Gruszynski’s cinematography makes everything look vaguely plastic and unreal. A real drawback, though, is Ralph Sall’s overbearing score, which at several points (a car chase and an absurd sequence involving a bomb, of all things) actually sounds like the stuff Ed Wood employed in “Plan Nine from Outer Space.”

“Nancy Drew” isn’t as bad as that, but far from being the studio’s fair-haired hope to anchor a new franchise to replace “Harry Potter,” it’s a cable-ready poor cousin to “Lemony Snicket’s A Series of Unfortunate Events,” which stalled after a single installment. We might not see another Nancy Drew movie for another 67 years—and maybe she’ll show up as a Miss Marple figure then.