Despite her doubts, firebrand Francesca Bruni (Sienna Miller) can't resist the overtures of Venice's notorious Casanova (Heath Ledger).

What happens in Venice stays in Venice.

Unless your name happens to be Giacomo Casanova -- and they've just made another movie about your storied exploits.

The real-life Casanova (as far as we can tell from his memoirs) led a life of infinite and fascinating variety -- and not just sexually, having pursued pursuits ranging from magic to literature to law to politics to philosophy to music to espionage to diplomacy.

This Casanova, however, leads a far less eclectic existence in 18th-century Venice. And if his reputation as a legendary lothario depended on the exploits depicted in this cheerfully rambunctious costume romp, nobody would make a movie about him in the first place.

But that's because this "Casanova" deals with more with love than sex.

Oh, Casanova ("Brokeback Mountain's" Heath Ledger, light years away from riding that melancholy range) has his share of close encounters, to be sure, and seems decidedly delighted to be engaged in such amatory matters.

That is, until he meets his match -- a proto-feminist firebrand (Sienna Miller) who masquerades as a man and pens best-selling philosophical treatises under a masculine nom-de-plume.

Additional cases of deliberate deception and mistaken identity crop up before "Casanova" finds its happily-ever-after.

And director Lasse Hallstrom (rebounding in bouncy fashion after the dreary likes of "An Unfinished Life" and "The Shipping News") seems only too happy to keep the merry-go-round spinning 'round.

It's 1753, and Casanova's the toast of the town, the scandalous inspiration for strolling players in St. Mark's Square -- and the object of lust among Venice's panting female population.

Alas, they're not the only ones after him.

The Roman Catholic Church also has its eye on Casanova for committing the crimes of "heresy and fornication" (not necessarily in that order). Repeatedly. And they keep hauling him -- repeatedly -- to the dungeon at the end of the Bridge of Sighs.

Luckily, Venice's reigning duke (Tim McInnerny) likes Casanova -- and likes rescuing the rascal from the church's draconian clutches. But things have gotten out of hand. Either leave Venice forever, the duke instructs our boy, or find a wife and settle down.

Leave Venice? Perish the thought. So Casanova and his invaluable manservant Lupo (the nimble Omid Djalili) begin the search for the ideal bride: one of Venice's few remaining virgins, the hot-to-trot Victoria (Natalie Dormer).

Their engagement enrages the boy across the canal, shyly romantic Giovanni Bruni (Charlie Cox), who's been pining for Victoria for ages -- and promptly challenges Casanova to a duel.

Giovanni's not much with the sword, unlike his big sister, Francesca (Miller), who disguises herself for the duel but eventually reveals herself to be Casanova's dream woman: beautiful (but of course), brilliant and utterly invulnerable to his romantic ministrations. The perfect catch has met his match.

Besides, Francesca's also got a fiancè. True, she's never met him. All she knows about Papprizzio (Oliver Platt) is that he's the lard king of Genoa. Which means that he may be a tub of lard, but he's more than able to keep Francesca, Giovanni and their widowed mother ("Alias' " Lena Olin, alias Mrs. Hallstrom) in the style to which they've become accustomed.

And if that's not a big enough carousel of complications for you, let's add one more to the merry mix: all the way from Rome, papal enforcer Bishop Pucci (Jeremy Irons), who's such a hard case he even has a crew cut atop his otherwise curly wig.

Clearly, this "Casanova" doesn't pay the strictest attention to historical detail.

In that sense -- and many others -- the movie recalls the playful, knockabout verve of Richard Lester's 1970s "Three Musketeers" romps -- or, more recently, the 1998 Oscar winner "Shakespeare in Love," without the soaring glories of the latter's Oscar-winning script. (The "Shakespeare in Love" connection may be more than coincidental; playwright Tom Stoppard, who co-wrote "Shakespeare," reportedly did an uncredited script polish.)

Another playwright, Jeffrey Hatcher ("Stage Beauty"), working with newcomer Kimberly Simi, whips up a genial mix of slapstick, frothy farce and scattershot satire, with a few courtly nods to notions of identity and the nature of love.

Hallstrom doesn't dwell on the latter, opting to keep the plates spinning while his all-star cast goes for baroque.

From Platt's pompous posturing to Irons' icy ire, the supporting cast supplies much of the movie's comic verve, while Miller makes a feisty, if occasionally strident, heroine.

And, providing comic contrast with his tragic turn in "Brokeback Mountain," Ledger's sly, insouciant Casanova emerges as a rapscallion of irresistible wit and charm -- who realizes, much to his surprise, that he's just as interested in love as he is in lust.