There's a moment early in the HBO documentary Going Clear — a rigorous, damning takedown of the Church of Scientology — when Lawrence Wright, on whose book the documentary is based, explains why he spent so much time and energy on his investigation. "My goal wasn't to write an expose," he says. "It was simply to try to understand Scientology."

Anyone who watches Going Clear will indeed walk away with a greater understanding of Scientology — but that doesn't mean they won't be enraged and horrified by it. This documentary, whose convincing allegations have been vetted by 160 HBO lawyers, might well turn out to be the last nail in Scientology's coffin.

As a piece of filmmaking, Going Clear is engaging but unspectacular. (If anything, the documentary's style is too on the nose; director Alex Gibney underscores many of the more bizarre bits with an eerie-sounding theremin tune, as if to say, "Get it? This is totally crazy!") The film's power is less about the originality of its content, most of which has been public for at least two years, and more about the impact of its form. Going Clear has condensed the original 560-page book into a two-hour movie. There's never been a version of this story that's so visceral, so accessible, and so succinct.

If you've spent any time reading up on the dark side of Scientology, you'll be familiar with much of what Going Clear reveals. Of course, that doesn't make the alleged details any less horrific or absurd: the billion-year contract signed by members of the Sea Org, who are paid 40 cents an hour for their menial labor; the pressure to have abortions because children are an "unpractical burden"; extreme punishments for perceived transgressions against the church, which include cleaning toilets with a toothbrush and cleaning a bathroom floor with a tongue; the stalking and harassment of ex-members and their loved ones, which continues for years after they leave the church; and the top-secret Scientology creation myth, taught only to high-ranking members, about an ancient alien overlord named Xenu who combated overpopulation by freezing his subjects and dropping them into volcanoes.

But while it may not break any new ground, the documentary's very existence is a kind of coup — a raised middle finger to the Church of Scientology, which has routinely used intimidation and a strictly enforced code of silence to squelch any public criticism. Alex Gibney and the half-dozen former Scientologists who spoke openly about their experiences have had their names dragged through the mud by the vengeful PR wing of the church. (As usual, church leader David Miscavige rejected an offer to be interviewed — his default response to any press inquiry that isn't explicitly pro-Scientology.)

In the months leading up to Going Clear's Sunday premiere, the Church of Scientology has resorted to the strategy pioneered by founder L. Ron Hubbard: "Never defend. We always attack." You can see the nadir of the church's anti-Going Clear tactics in the ludicrous, Scientology-funded Twitter account @FreedomMediaEthics, which has been relentlessly campaigning against Going Clear. For weeks, I've had @FreedomMediaEthics tweets pushed into my Twitter feed as paid sponsored content, smearing the names of pretty much everybody involved in the production of Going Clear. (For the record: I spent a fair amount of time clicking around the church's anti-Going Clear websites, and the attacks are uniformly petty and unconvincing.)

This is a classic Scientology tactic: a forceful, aggressive, and presumably expensive campaign designed to discredit anyone who dares to speak against the church. But a funny thing happened with @FreedomMediaEthics: nobody cared. As of this writing, the account sits at a miniscule 501 followers. The promoted tweets — like this one — have been singled out for widespread derision, with dozens of annoyed Twitter users attacking the account for its ad hominem attacks on Going Clear and its participants.

All those derisive tweets are fascinating in contrast to the emotional interviews that make up the backbone of Going Clear. Former Scientologists recount horror story after horror story about the church's vengeful backlash against anyone with the temerity to speak against it. Many of them remain afraid. But the church's power always relied on its ability to control the flow of information, both within and outside the church, and today, that's simply impossible. There was a time, just years ago, when Scientology could successfully recruit members with the bait-and-switch of a "personality test." Paul Haggis, the film director and former Scientologist, says he spent seven or eight years and hundreds of thousands of dollars to reach the level at which he was permitted to learn Scientology's ridiculous creation story. Today, anyone in that same position can click over to Wikipedia, or queue up an episode of South Park — or, starting on Sunday, watch Going Clear.

Maybe that's the reason that in every metric but money, the church's power is clearly waning. Going Clear estimates that the Church of Scientology's membership has declined to around 50,000 members. There's a strong case to be made for revoking the Church of Scientology's religious tax exemption, which was obtained by strong-arming the IRS with 2,400 costly lawsuits filed by members of the church. That tax exemption saved the Church of Scientology from going under; under the terms of the deal, the IRS forgave a billion-dollar debt amassed by L. Ron Hubbard, who refused to pay taxes, and enabled the church to acquire billions of tax-free dollars in donations and real estate holdings. Even the earnings from L. Ron Hubbard's novels are treated as non-taxable religious documents. "The war is over," announced David Miscavige in a triumphant speech announcing the church's newly legitimized status.

Of course, tax exemptions are granted to religious organizations that are serving some kind of public good, and it's hard to imagine anyone walking away from Going Clear with the belief that Scientology is anything but a negative force in the world. The documentary is likely to stir outrage — at the leaders of the church, at celebrities like Tom Cruise who perpetuate its influence, at the IRS officials who allowed themselves to be browbeaten into legitimizing and empowering such a dangerous organization. "I'm fighting back by communicating," says one ex-Scientologist at the end of the documentary. With Going Clear, that fight is going mainstream, and a lot of people have a lot to answer for.