In the town on the southern coast of England in which David Leland's "Wish You Were Here" is set, the grayness of the sky and the sea and the weathered storefronts seems more than simply an attribute of weather. The people seem grayed-out, too, as if a sprinkling of ash had settled over them.

The only splash of color is Lynda (Emily Lloyd), a robustly perverse teen-ager who's the daughter of the local barber (Geoffrey Hutchings). In contrast to her surroundings, everything about Lynda is bright, vivid, alive. When we first see her she's flying down the boardwalk along the beach on her bike, wind in her hair, the hem of her skirt stuffed up into her underwear so that a generous portion of leg is displayed. The color of the skirt -- a cotton-candy pink that matches her lipstick -- is perfect. It brings out the glow in her cheeks and makes her look lusciously ripe, like a peach about to fall from its branch. Whizzing about, she seems winged, untamable.

On the handlebars of Lynda's bike is a periwinkle-colored pinwheel, spinning freely as she breezes along, and that's her symbol. Set in 1951, the movie is about a young girl who uses sex to shock, and how these shocks, liberally administered, keep her spirit alive. As Lynda, Lloyd is a raging malcontent -- an angry young brat. But her anger doesn't manifest itself in conventional ways. (Nothing in her personality does.) Instead of fevered rants, Lynda peppers her targets with a nonstop barrage of hilarious obscenities. These blistering attacks aren't contrived; they just bubble out of her, and it seems never to have crossed her mind that she might censor herself. Not censoring herself, in fact, is what keeps her going; it's what keeps the pink in her cheeks.

Lynda has a genius for the profane mot, and she uses it indiscriminately. And as we learn from flashbacks, she started early. On the day her father returned from service in World War II, she shocked him and his guests by whispering a pungent aside to her little sister, who dutifully reported it to the others in the room. (This is after greeting him on the front steps wearing a gas mask.)

But Leland establishes a deep empathy with his heroine, and, seeing through the little girl's eyes the look of suffocating boredom on her mother's face as she portions out the tea and biscuits, we can immediately see the purpose served by her rebellious, briny outbursts. The mother died when Lynda was only 11, and it's to this lost parent, the one who might have been able to understand her and help her through her troubles, that the film's title is addressed. And Leland never lets us forget that there's something broken rattling around inside Lynda, and that this, in part, is what's making all the noise.

Leland is particularly shrewd about this aspect of Lynda's character. He doesn't attempt to rationalize her behavior or categorize her problems. And when she wags her bum at the doctor and her father, or perches on top of an office desk in the bus depot where she works to give the workers a look at her new knickers, he doesn't attempt to romanticize her into a symbol of liberated nonconformity. That he leaves open the possibility that there may be more than a touch of pathology in Lynda's behavior, that her free-spiritedness is not only the mark of a rebel but also a sign of deep resentments and anger, gives her greater dimension. Making her a heroine would diminish her, so Leland gives her to us straight -- mixed-up, antagonistic, self-centered, captivating.

Leland never loses his comic footing either. He has a real talent for sexual slapstick. In common parlance, Lynda might be called a problem child. Her father, not knowing how to deal with her sexual frankness, thinks there's something wrong with her, that she's genuinely afflicted. This assumption gives occasion to the film's funniest scene, a visit to a wild-haired psychiatrist who questions her, in a modulated, dispassionate manner -- the manner of a biologist inspecting a slide -- about her filthy mouth. Nervously chain-smoking and trying desperately to retain the upper hand, the doctor prods her to run through the alphabet, starting with "A" ("Best place"), listing all the dirty words she knows. Appearing to take the bait, Lynda complies, but quickly turns the tables on him, and the scene escalates into a sublime bit of pyscho-burlesque, a sort of Freudian "Who's on First."

"Wish You Were Here" is really Lloyd's movie, and the prospect of finding a performance like the one she gives here is one of the main reasons why people still get excited about going to the movies. As Lynda, Lloyd is so fresh that she seems almost downy, newly hatched. This is her first movie role -- she was just 16 when the film was made -- but she's so sassy and unaffected that you'd think she's been acting for years.

Lloyd's features are open and inquisitive and just slightly unformed; she hasn't quite grown into her face yet, and that makes her perfect to play Lynda. Lloyd has an instinctual vivacity on screen, a natural glow.

Everything about Lynda is rooted in sex, but without being overtly sexual. At 16, Lynda is still a mere chick, but already she appears to have taken in a lot. In the actual sense, Lynda has almost no experience of sex. But she's an eager initiate. Too impatient to wait for a boy she's interested in to ask her out, she skips the usual courtship protocol and tells him, flat-out, she fancies him and does the asking herself, flashing a bit of thigh as enticement.

Still, though she's clear-eyed about sex, everything seems brand new to her. Just walking along in spiky heels and seamed stockings, she's swept away by the sensations she feels, and the idea that she can provoke men by twitching her hips makes her nearly dizzy with excitement. She's revved up about life, about sex, about whatever's around the next corner, and she can't wait to get started.

Lynda's got energy to burn, but there's no outlet for it in her musty, provincial hometown. Her naughty high jinks are her only form of self-expression, and one night in the back yard, filled with profane abandon, she improvises a bawdy dance set to the music of her favorite obscenity, and fully unfurled, she seems truly inspired -- the Isadora Duncan of smutty outrage.

It's Lynda's rambunctious, self-destructive exuberance -- the sense that she's a genuine misfit -- that makes this more than a routine coming-of-age story. Lynda is a rich, spirited creation, and Leland's work here, as both screenwriter and director, is sharp and evocative. This is his first time out as a director -- he's been known previously as the screenwriter on "Mona Lisa" and "Personal Services" -- but he shows here as he did in his earlier scripts that he knows how to make sexual tension funny.

In addition, in the scenes involving Eric (Tom Bell), a bookie and the operator of the local cinema, Leland shows a talent for capturing the pathos in squalor. When the older man -- Bell is in his fifties -- seduces Lynda, the movie turns abruptly down a darker, creepier road, but Leland retains control, and he shows how Eric's bluish stubble, his slitted, blurry eyes, and the slummy disarray of his flat above the movie theater combine to form a picture of a rake come to ruin.

The moody second half of the film, though, isn't as compelling or original as the first. For a good portion of it, Lynda plays Lolita to Eric's Humbert, but though it's clear that she is impatient with her younger, less experienced partners and could use a more practiced hand, it's not immediately obvious what this spectacular girl sees in her seedy scarecrow lover.

The ending, too, which presents Lynda as a triumphant heroine in the style of the postwar movie stars whose stories she watched at the local theater, is not entirely satisfying. Not that you want to see her come to a bad end. But as it stands, the finish is too conventional, too pat.

These are quibbles, though. "Wish You Were Here" is an impudently sexy comedy, and both the director and his young star have made auspicous debuts. Even the neatness of the ending doesn't really throw you off much. For this film, Leland has used some of the details from the early life of Cynthia Payne, the famous madam who served as his model for "Personal Services," and you want her to prevail, to cut loose. It would be too much of a letdown to leave Lynda grounded and sorrowful; after watching her crash rudely, blithely about, upsetting tea rooms and scandalizing stuffy matrons, the last thing you want is for her to pay for her eccentricity.

Wish You Were Here, at the Circle West End, is rated R and contains profane language and some suggestive material.