ALEX GIBNEY is a documentary filmmaker known to have specialised in finding skeletons in cupboards. The skeletons in Going Clear: Scientology and the prison of belief (Cert. 15) make as interesting, not to mention chilling, a film as his Mea Maxima Culpa, about Roman Catholic clerical abuse (Arts, 15 February 2013).

The Church of Scientology believes that human beings need to recover their true nature through processes such as "auditing" painful experiences. Going clear is the stage reached when followers move from their present state to greater self-awareness. Scientology's notoriety stems from its methodologies and financial practices. The documentary seizes on these aspects, interviewing former Scientologists who use words such as "brainwashed", "fleeced", and "intimidated" to describe their encounters with this faith.

Going Clear's reliance on public figures such as the film director Paul Haggis (Crash), as well as ordinary people who temporarily became involved with this rich, tax-exempt organisation, may seem a little one-sided. The failure to meet a single current member has fuelled the organisation's campaign to discredit the film. Gibney defends this omission, saying that he feared an ambush, not a dialogue.

We do get scenes, culled from library clips, involving practitioners such as the actors Tom Cruise and John Travolta. Given how litigious the Board of Religious Technology, Scientology's official title, can be, it is unsurprising that the film was vetted by 160 lawyers before its HBO screening on US television. Lawrence Wright's book of the same name, on which the film is based, was never published in the UK after Scientologists threatened legal action.

The price apostates have paid has often been very high: marriages and families have broken up, personal reputations have been destroyed, and people have been left in fragile states of mind. Scientology has labelled these damaged personalities as unreliable witnesses. It also took exception to the director's inserted footage of a Nazi concentration camp when one ex-member described Scientology as a prison.

Even so, the film is an amazing portrayal of religion's power to entice seemingly level-headed people into an initially attractive lifestyle that promises that the next stop is infinity.

This documentary, high on facts, also crosses into feature film through dramatised re-enactments. That may be OK, but The Master (2012), inspired by Scientology's founder, L. Ron Hubbard, does it even better. That is because drama is relatively free of legal constraints and, more importantly, provides an emotional depth through its characterisations which Gibney's craft, considerable though it is, cannot match.