Based on the original mystery book series by Mildred Wirt Benson, "Nancy Drew" has been updated to modern times, but doesn't lose sight of what made the savvy teenage sleuth such a hit with young readers throughout the last eight decades. And, lest loyalists start crying foul, she is rarely without her tidy wool suits, sophisticated dresses, investigative tool kit and penny loafers. As directed by Andrew Fleming (2003's "The In-Laws"), "Nancy Drew" is a genial and fast-paced family film, as light as cotton candy but sure to win over its target audience of pre-teen girls. For everyone else, it is a painless lark that is much less sugarcoated than it could have been.

16-year-old Nancy Drew (Emma Roberts) is something of a star in her small town of River Heights, a makeshift detective who manages to catch all the criminals that the police force can't. When she and her dad Carson (Tate Donovan) uproot themselves to Los Angeles for the summer, he makes her promise that her undercover days are behind her. Nancy tries to make good on this vow, but it proves impossible after they move into a long-abandoned Hollywood mansion once owned by glamorous movie star Dehlia Draycott (Laura Elena Harring). Dehlia had the world at her fingertips back in the '60s and '70s, but then disappeared without a trace. Upon her sudden return, she was found dead in the swimming pool. With adoring 12-year-old Corky (Josh Flitter) frequently by her side, Nancy sets out to investigate Dehlia's death and locate the newborn daughter she gave up for adoption twenty-five years ago. When someone tries to run her over in their car, however, it immediately becomes apparent that people with a connection to Dehlia don't want Nancy digging up the past.

The mystery plot that screenwriters Andrew Fleming and Tiffany Paulsen have devised for the inaugural cinematic "Nancy Drew" outing isn't particularly well thought-out. For a lot of the time, it is never made clear exactly what Nancy is searching for, and why. Since Dehlia's death isn't confirmed to be a murder, the movie isn't really a whodunit, and when she tracks down the late star's long-lost daughter Jane (Rachael Leigh Cook), it is confusing how she could be of help since she previously had no idea of her mother's identity. Nevertheless, the movie coasts along on sheer good will and Nancy's intriguing investigative prowess. When Nancy is put in harm's way, as when a van tries to run her off the road or when she is being chased through the secret passageways beneath her house's property, the film doesn't soften the endangerment. This seriousness gives the story a levity and, insomuch that it can, a realistic undercurrent.

That is not to say that "Nancy Drew" is all business and no play. The humor comes at a fairly steady rate, and there are a number of mischievous laughs to be found that prove director Andrew Fleming is in on the joke. When a creepy neighbor named Mr. Leshing (Marshall Bell) suddenly pops up and startles Nancy upon her arrival at the mansion, the real estate agent (Caroline Aaron) introduces him as "the strange undertaker who lives in the guest house down the hill." Also funny is a run-in with Bruce Willis while he is shooting a picture in downtown L.A., and the sweet ongoing interplay between Nancy and semi-partner Corky, who is enamored by this older girl and none too pleased when her close friend from River Heights, Ned Nickerson (Max Thieriot), pays a surprise visit for the weekend.

Emma Roberts (2006's "Aquamarine") isn't the most adept or skillful of today's younger actresses, but the resourceful role of Nancy Drew fits her like a glove. Roberts embodies Nancy's prim and proper attitude without making her seem snooty, and when the circumstance calls for it, she's not afraid to get her hands dirty. As Corky, Josh Flitter (2006's "Big Momma's House 2") is a scene-stealer with on-target comic timing. He's also adorable without being annoying, and is an ideal cohort for Nancy. Less endearing is Max Thieriot (2007's "The Astronaut Farmer"), whose Ned is written and performed like a stick in the mud. It would have been beneficial to portray him as a more venturesome type since he is supposed to be Nancy's love interest. As is, the viewer isn't quite sure what she sees in him.

"Nancy Drew" was attractively lensed on-location in Los Angeles by cinematographer Alexander Gruszynski (2003's "Deliver Us from Eva"), and the use of a number of recognizable landmarks contributes nice background shading. As Nancy gets to bottom of the questions surrounding Dehlia Draycott's life and death, the answers don't make the same impact as the journey does. The sleuthing itself is where the fun is at, and "Nancy Drew," while not about to set cinema screens on fire, is enjoyable enough for one to hope there are more onscreen mysteries for her to solve in the near future.