Which witch is wicked? A smart new musical turns The Wizard of Oz on its head with its tale of a good witch who knew too much.

Wicked is that rarity, a Broadway musical with intellectual substance --even if it comes disguised as fairy-tale entertainment that pays satirical homage to The Wizard of Oz. Like. the book by gay novelist Gregory Maguire on which it is based, the show gives the VH1 Behind the Music treatment to the Wicked Witch of the West, going back to the beginning and filling us in on everything that happened to her before she crossed yellow brick paths with a little girl from Kansas played by Judy Garland.

In this version, the WWW begins life as a freak named Elphaba (Idina Menzel). She's born green and suffers all the childhood agonies of being different, which instills in her a natural affinity for the underdog. In college she's thrown into rooming with Galinda (Kristin Chenoweth), a rich would-be sorcerer bristling with blond ambition, whom other kids revere as automatically as they reject Elphaba.

Almost despite themselves, these two rub off on each other. Elphaba gains some of Galilnda's self-confidence, especially regarding her magic powers, and Galinda (who will, of course, become Glinda) finds herself doing good deeds in her own way.

In a pretty explicit reference to the U.S.'s current penning-up of Arab suspected terrorists at Guantanamo Bay, the animals of Oz are being caged and deprived of the power of speech. When Elphaba's powers bring her to the attention of the Waizard (Joel Grey), she's thrilled, thinking they can join forces to fight these threats to freedom. But she discovers he's a fraud who controls his subjects through fatuous happy talk. That makes her dangerous--and the campaign to brand her as wicked spreads faster than you can say Karl Rove.

It's a trippy experience to watch a musical comedy that invites your brain to stay busy translating the subtext. Wicked shows the perils of turning the polarities of human nature--good and evil--into opposites--good or evil. It's also a plitical fable that asks, When we're looking at what They want us to look at, what are we ignoring that They want us to ignore? Thematically, you could say it's Into the Wood's meets Wag the Dog.

Meanwhile, director Joe Mantello puts on a visually dazzling and imaginative show. Stephen Schwartz's score is musically undistinguished but dramatically effective, and the book by Winnie Holzman (My So-called Life) takes many sharp, funny turns. Idina Menzel is a powerful Elphaba--imagine Tori Amos as Thoroughly Green Millie--but Kristin Chenoweth can't help stealing the show with a postmodern Glinda who borrows heavily and enjoyably from Will & Gerace's Karen. From the moment she appears in a high-tech bubble and coos, "It's good to see me, isn't it?" she perfectly embodies the picture-pointing-the-frame perspective of this weird, smart musical that's definitely worth seeing.

Shewey writes on theater for The New York Times.