Oh, what a tangled web Spider-Man 3 is! The new chapter in one of the most delightful movie superhero franchises of all time is considerably stickier than the previous high-flying adventures, straining to give audiences more of everything, to diminished effect. There's more mayhem, more darkness, more outrageous villains, more romantic complications, but far less of the charm that's helped make the series such a record-setting success.

The continuing story of nerdy Queens, New Yorker turned super-powered crime-fighter Peter Parker (Tobey Maguire) begins in a deceptively placid mood, as Peter gets ready to propose to his longtime love, Mary Jane (Kirsten Dunst), who's realizing her dream of starring on the Broadway stage. But things quickly go sour: Peter's onetime friend Harry Osborn (James Franco), who blames Peter for the death of his demented super-villain dad, re-emerges in his own evil guise as the New Goblin and ambushes Peter in an aerial battle before being knocked unconscious and losing all memory of his grievance. Mary Jane's taste of fame is fleeting when she gets terrible reviews and is fired from her show. And, oh yes, a meteor crashes to Earth and emits an ominous black substance whose first target is none other than the spectacularly unlucky Peter.

And let's not forget the emergence of yet another super-villain, Flint Marko (Thomas Haden Church), an escaped convict who has the misfortune to take refuge in a high-tech research facility and be caught in a molecular-fusion experiment that turns him into a shape-shifting sand monster. Late in the game, a third ultra-nemesis enters the mix when Eddie Brock (Topher Grace), a sleazy photographer rival of Peter's at the Daily Bugle, falls victim to the black stuff and transforms into the vicious, sharp-fanged Venom.

By that point, the alien substance has already had a profound impact on Peter, who becomes vulnerable to his worst impulses once he learns that Flint is the man who killed his beloved Uncle Ben, not the criminal dispatched in the first film. As his relationship with Mary Jane collapses (partly due to her jealousy over his stardom, bane of many a Hollywood couple), Peter opts for fashionable black over red in his superhero duds and, in civilian dress, combs down his hair and acts like a "hipster doofus," in the immortal words of Elaine Benes. Peter, of course, eventually comes to reject the dark side, but will he have the stamina to save Mary Jane from the formidable tag team of Sandman and Venom?

Director Sam Raimi and his brother Ivan have concocted an overcrowded narrative that lurches from one set-piece to another, some of them admittedly spectacular. Two of the best happen early on: an out-of-control construction crane crashing through a skyscraper and imperiling the life of Gwen Stacy (Bryce Dallas Howard), who just happens to be Peter's college lab partner and the daughter of an NYPD captain; and Flint's sensational transformation into Sandman. But for every exciting special-effects sequence, there's another scene of dull romantic angst right out of an episode of "Dawson's Creek." Part of the attraction of the first two films was the balance they struck between the comic-book acrobatics and the down-to-earth human element. Here, with Mary Jane sullen and depressed through most of the movie, the human moments are simply earthbound.

Maguire somehow still makes us believe in the goofy innocence of Peter Parker, and it's fun seeing the character attempt to emulate badass attitude. The new additions to the cast are also a plus: Haden Church conveys a truly haunted quality as Flint; Grace again proves himself a devilishly graceful young comedian; and "Lady in the Water" Howard, here a platinum blonde, is a truly vivacious Gwen. Longtime Raimi cohort Bruce Campbell also has an entertaining cameo in the unlikely role of a French maitre d'.

At a reported minimum of $250 million, Spider-Man 3 is one of most expensive movies ever made, and there's enough big-scale production value and visual-effects magic to engage genre fans worldwide. But Raimi and company have woven more graceful patterns in the past; this one simply doesn't cohere.