PARK CITY, Utah Secrecy shrouded the controversial documentary "Going Clear: Scientology and the Prison of Belief" when it premi�red at the Sundance Film Festival.

Rumours swirled about massive protests, prompting filmgoers to arrive hours in advance to assure they got a seat.

Security was heightened, but no threats materialized.

The festival's most hotly anticipated documentary did not disappoint, however. The revelations were almost as numerous as the number of lawyers HBO Documentary Films hired to vet the movie (160).

The scathing expos� directed by Alex Gibney ("The Armstrong Lie") is based on Lawrence Wright's riveting 2013 bestseller.

Among the bombshells asserted by eight former church members: Scientology intentionally broke up Tom Cruise and Nicole Kidman; it tortured some of its members in a prison known as "the hole" and subjected others to hard labour; it harassed those who left the organization and forced their family members to cut off all contact.

The film offers an intimate portrait of founder L. Ron Hubbard (or LRH as he's referred to by members) and follows the rise of current leader David Miscavige, alleging his misuse of power and that he physically abused several members.

The film also claims that Hubbard beat and threatened his first wife and kidnapped their daughter, leaving her in Cuba in the care of a mentally disabled woman. It also detailed Hubbard's elaborate cosmology incorporating space aliens, invading spirits, volcanoes and other elements that his sci-fi writing had contained.

One of the former members interviewed, Marty Rathbun, was the second highest-ranking church official before he defected. He alleged that Miscavige didn't approve of Kidman because her father is a well-known psychologist in Australia, and Scientology vehemently opposes psychiatry and psychology.

The film goes on to explore the close friendship between Miscavige and Cruise, and questions whether Cruise is aware of church abuses. The filmmaker essentially calls upon Cruise to renounce Scientology in order to put a stop to the abuses.

It also alleges that another high-profile member, John Travolta, won't leave the church out of fear that his personal life will be exposed. Reams of information are kept on each member as they go through the process of "auditing" in order to become "clear" of all problems, worries and bad memories.

Spanky Taylor, a former publicist and friend of Travolta, details how her infant daughter was taken away from her and left in a urine-soaked crib and unsanitary, fly-infested conditions. Meanwhile, Taylor was forced to do arduous physical labour while she was pregnant. Fed up, Taylor took her child and escaped from the church. She attended the premi�re with her now-grown daughter Vanessa, whom Gibney called "the stolen baby."

Several of the former members who spoke out in the documentary - and also in Wright's book - were on hand for the Sunday premi�re, and drew a standing ovation.

"You're so thoroughly indoctrinated, deluded and not questioning anything because (Hubbard) had all the answers," said Taylor. "So you continue to believe all the nonsense."

Gibney said he has received "many cards and letters" from Scientology's lawyers.

"The kinds of threats that I've received, and Alex as a filmmaker, have been predominantly legal and they have been manifold," said Wright. "But nothing compared to what the people who were in the church suffered."

Wright lauded those who spoke out in the documentary. "I want to emphasize what a tremendous amount of courage it took for people to come out," he said. "The goal was to get as many people to talk so they'd feel safe in numbers."

The film reveals the church to have fewer than 50,000 members worldwide but more than $1 billion in assets.

The former members interviewed, including screenwriter Paul Haggis and others high up in the organization, described how they turned over vast sums of money to the church. They used terms like "brainwashing" and each expressed remorse and chagrin over their involvement with the organization, which was granted church status by the IRS in 1993, making it tax-exempt.

Scientology's fight against the IRS was detailed, as was a lavish celebration thrown by Miscavige and Scientology officials when the "war" with the federal government ended in the group's victory.

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The film also featured moving emotional testimony from a lifelong member who had achieved the highest status in the church, but left when her son was labelled "a suppressive person." The organization demanded that her daughter, still a member, and granddaughter, cut off all contact.

"The hope of this film is that it will raise public awareness," said Gibney.

"Going Clear" is scheduled to air on HBO later this year.