"Hair" is back in a blistering, take-no-prisoners London update that lands the 1967 musical firmly in 2005. Purists may resist director Daniel Kramer's extensive rewrite of what, truth to tell, had devolved into a fairly trying period piece. But what's amazing is that this "Hair" is in every way true to the spirit of the show, if not always the letter.

Nearly four decades after the countercultural touchstone helped define the flower-power era, “Hair” is back in a blistering, take-no-prisoners London update that lands the 1967 musical firmly in 2005. Purists may resist director Daniel Kramer’s extensive rewrite of what, truth to tell, had devolved into a fairly trying period piece. But what’s amazing is that this “Hair” is in every way true to the spirit of the show, if not always the letter. If the Galt MacDermot/Gerome Ragni/James Rado original was spawned both in hopefulness and sorrow, so is a 21st-century version that starts from a place of anger only to allow for the possibility of exultation.

Kramer’s contribution to the Ragni/Rado book has gone uncredited, but there’s simply no way to separate the impact of this production from the wholesale overhaul to which its fast-ascending 27-year-old American director has subjected the material.

Returning to London’s Gate Theater, where he is now an associate director, Kramer proves his dizzying Gate revival of Buchner’s “Woyzeck” was no fluke. He takes his audience on a wild ride, and one’s only regret is that the theater’s tiny seating capacity (a scant 65) means more people won’t be able to come along for the journey. (Production is angling for a transfer, though any subsequent venue will be hard-pressed to match the Gate’s spectacular intimacy.)

There are multiple shocks generated by a “Hair” that, among other things, dares to reimagine the show’s defining nudity as part of the collective abasement at Abu Ghraib. Then again, this “Hair” actually takes seriously the citations from “Hamlet” that inform “What a Piece of Work Is Man,” to name one of the more plaintive melodies of MacDermot’s still-transporting score.

As played by beautiful, bleach-haired newcomer Charles Aitken, the show’s central figure, Claude, really is a modern-day musical theater Hamlet for our mournful age of Dubya, terrorism, the war in Iraq and AIDS. (Gary Amers’ free-loving Woof has H.I.V.I.P. tattooed on his chest and delivers “Sodomy” while straddling a friend atop a giant swath of latex.)

Whereas generations of scholars have debated whether Hamlet was sick or slick, the question asked of Claude is whether this angel-faced lost soul is headed for “greatness — or madness.” “Greatness,” comes the immediate reply of the Tribe, the NYU community who want to shield Claude from the abrasions of a war to which he seems entirely devoted. (His view of the Iraq conflict: “People who once weren’t free are now free. End of story.”)

So, has “Hair” gone soft? Not at all. The anti-establishment vigor is evident in the zest with which Claude belts out “I Got Life” in front of his unthinking parents: As before, he’s a native of Flushing, Queens, in emotional thrall to Manchester, England. But the point is to make this addict of “Prince Prozac” an emblem of a confused time whose capacity for nihilism has increased exponentially since “Hair’s” Off Broadway preem.

No wonder the startling opening scene finds “Aquarius” delivered via megaphone to the scurrying, anonymous inhabitants of a jittery Times Square. In Kramer’s rewrite, Berger (Kevin Wathen) first espies Donna (she of the famous song lyric) through an “industrial 9/11 haze.” This leaves Sheila (Joanna Ampil) later to attempt to slice through the psychic fog by leading a piercing rendition of “Good Morning Starshine”: a happy-clappy lovefest turned call to emotional arms.

The result quite rightly ditches the feel of an original book that seemed to have been written on the back of “Rowan & Martin’s Laugh-In” and that has sunk “Hair” in many previous revivals.

Though the visual iconography of Soutra Gilmour’s design is unexceptional, Ann Yee’s choreography takes its abiding cue from “Walking in Space.” More than once, the cast seem propelled through the Gate’s rectangular playing space as if on an adrenalized journey that keeps pulling them up short into a kind of drugged-out moonwalk. What, after all, is worth searching out in a corporate America that, in this staging, finds the chilling smile of George W. Bush (Graham Tudor is a Paul Lynde look-alike in the role) at every turn — Condi and Rumsfeld ready by his side?

Not that “Hair” settles for cynicism. What’s especially bracing about Kramer and his largely wonderful cast (Nancy Wei-George’s Crissy is a human fireball) is that a show conceived on one level in rage still beats to so tumultuous a heart. Sure, some passages are messy and not every rethink lands, and what seems galvanic in so small a space could curdle into pretension in a larger venue.

But Kramer has reinvented an American musical icon from the inside out for a post-Aquarian age in which, one hopes, it’s never too late to love.

Hair

Gate Theater; 65 Seats; £20 ($35) Top

Production

A Gate Theater production by arrangement with Musicscope and Stage Musicals Ltd. of New York of a musical in two acts with music by Galt MacDermot, book and lyrics by Gerome Ragni and James Rado. Directed by Daniel Kramer. Musical director, Steve Hill. Choreography, Ann Yee.

Creative

Sets, Soutra Gilmour; costumes, Penelope Challen; lighting, Charles Balfour; musical supervisor, Stephen Brooker; sound, Mick Potter; assistant director, David Dorrian. Opened, reviewed Sept. 22, 2005. Running time: 2 HOURS, 30 MIN.

Cast

Claude - Charles Aitken Woof - Gary Amers Sheila - Joanna Ampil Berger - Kevin Wathen Hud - Golda Rosheuvel Dionne - Lee Reynolds Crissy - Nancy Wei-George George - Graham Tudor Jeanie - Robyn Isaac
With: Craig Perry, Sean Parkins, Laura Selwood, Miriam Elwell-Sutton, Connor McAllister, Stuart Armfield, Kate Gillespie.
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