Rock the Bells, the new documentary by Denis Henry Hennelly and Casey Suchan, captures the moment with stunning clarity, and though it offers a richly satisfying climax, the journey to that point is anything but smooth. When promoter Chang Weisberg first set out on his mission to reunite the Wu-Tang for his 2004 hip-hop festival in San Bernardino, he knew he was up against tall odds, given the Clan’s reputation for no-shows and infighting. But, to paraphrase fictional Spinal Tap director Marty DeBergi, he got more, much more, than he bargained for.

Among his headaches revealed in the film: Inadequate security; local authorities who want no part of a hip-hop festival and the drug culture they believe it promotes; impatient fans crashing the gates; and at least one performer, Redman, who refuses to cooperate “without no herb.”

And that’s before one of the Wu-Tang’s massive entourage drops the bomb: Ol’ Dirty Bastard, arguably the most beloved and unquestionably the most troubled member of the Clan, has passed out in his hotel room and cannot move. An intriguing power play ensues, with Wu-Tang founder RZA (the only member who seems to grasp the gravity of the situation, as thousands of fans seem poised to revolt if the Clan doesn’t go on) begging and eventually bribing ODB’s handlers into producing their man. He shows up, in body if not in mind, sitting atop a speaker with his eyes closed for most of the band’s two-hour-plus set.

It is during the film’s final hour, as momentum builds toward a reunion that remains in doubt until the moment all nine original Clan members (with on-again, off-again contributor Cappadonna) step to the mike, that Rock the Bells takes its place alongside the very best concert documentaries. There are lighter moments that would feel right at home in comedies like Spinal Tap, as when one production assistant attempts to sum up his motivation for staging the show. (“Chang has a vision,” he explains. “I don’t necessarily know what that vision is.”) But there is real, gripping drama, too, reminiscent of even the peerless Gimme Shelter.

It’s obvious from the start that Chang is headed for trouble, given his naïve decision to discourage police participation and his grossly undermanned security team. Indeed, violence casts an almost palpable pall over the proceedings as the crowd surges and demands the reunion it paid for, even as some of the main players saunter about indifferently backstage. The ending is both a relief and remarkably incident-free, but not without a heartbreaking postscript: Four months after the Wu-Tang’s triumphant return, ODB overdosed and died in the band’s 36 Chambers studios.