A Four Corners investigation airing on Monday night is set to share disturbing allegations made by dozens of students from private schools in Sydney affiliated with the religious group Opus Dei.
While the group is known for its secrecy, it's far from the first time it has appeared in the headlines.
So what exactly is Opus Dei, and why is it so controversial?
What is Opus Dei?
Opus Dei is a small but powerful organisation within the Catholic Church officially known as the Prelature of the Holy Cross and Opus Dei.
Its members believe they are called to serve God not just through personal spiritual acts, but also through how they conduct themselves in their professional and family lives.
They abide by strict conservative teachings and generally maintain a level of secrecy, often choosing not to volunteer their membership to people outside the church.
Opus Dei is notable for being the Catholic Church's only "personal prelature", meaning its global membership is determined by personal criteria instead of a geographical area, as would be the case with a local diocese.
Its special status has invited controversy, with some Catholic scholars likening it to a "church within a church" and criticising the amount of influence it wields.
Who founded Opus Dei, and when?
Opus Dei was founded in 1928 by Josemaría Escrivá, a Spanish Roman Catholic priest who said he had received a vision of its creation from God.
Escrivá maintained throughout his life that the group's creation was not his work but was divine in nature.
In fact, Opus Dei means "Work of God" in Latin.
He was beatified in 1992 and canonised in 2002 by Pope John Paul II, who deemed him the "saint of ordinary life".
How many members does Opus Dei have, and what do they do?
The Catholic Church's Annuario Pontificio (Pontifical Yearbook) for 2022, its most recent publication, says there were 93,510 members of Opus Dei worldwide as of 2021.
That number is comprised of 2,115 priests and 91,395 lay people, or regular, non-clergy members of the church.
About 650 members of Opus Dei are believed to live in Australia.
Most of the group's lay people are supernumeraries or numeraries.
Supernumeraries make up the majority of the group's membership, estimated at about 70 per cent.
Typically people with regular careers, supernumeraries are encouraged to marry, have a family and live otherwise regular lives.
They contribute financially to Opus Dei, engage in prayer and attend meetings and retreats.
Many of the remainder of the membership, about 20 per cent, are numeraries — celibate men or women who have chosen to make themselves fully available to undertake Opus Dei's work.
While some numeraries have jobs that they fit around their work for the church, the majority of them live in special centres run by Opus Dei and devote most of their time to serving the group.
Why is Opus Dei controversial?
Opus Dei's secretive nature has attracted criticism since its early days, with other Catholic groups, in particular the more liberal Jesuits, likening it to having Freemasons or the mafia operating within the church.
Its recruitment practices have been criticised, with critics and former members claiming it aggressively targets young people.
Opus Dei's ultra-conservative teachings have also garnered controversy, even among Catholics.
Numeraries and other celibate members of the group practise corporal mortification, the deliberate experience of pain or discomfort so as to become closer to God.
Distinct from other, more widely practised forms of religious mortification such as fasting on certain days, corporal mortification often involves wearing painful items of clothing such as a cilice, a small, spiked, metal chain wrapped around the thigh.
People who take part in corporal mortification may also choose to use a small, corded rope whip known as a discipline to self-flagellate.
In addition, some say Escrivá expressed support for far-right governments, in particular the fascist Franco regime in Spain under which he lived for several years.
Defenders of Opus Dei point out that freedom of choice in public life is emphasised in its teachings, and many notable Opus Dei members were critics of Franco.
What's the deal with the albino monk?
Opus Dei received a heightened level of public attention after the release of Dan Brown's novel The Da Vinci Code in 2003, and the subsequent film of the same name in 2006.
One of the story's major antagonists was an albino monk who was a member of Opus Dei and practised an extreme form of self-flagellation, whipping himself bloody to purify himself.
While it's entirely possible there are albino members of Opus Dei, there are, in fact, no monks or nuns in the group, which it went to great pains to point out in a statement posted to its website in 2005.
"The Da Vinci Code's depiction of Opus Dei is inaccurate, both in the overall impression and in many details," the statement read.
"It would be irresponsible to form any opinion of Opus Dei based on reading The Da Vinci Code."
The group also took issue with the book's depiction of mortification, saying its description of the cilice and discipline was "greatly exaggerated" and "it is simply not possible to injure oneself with them as [The Da Vinci Code] depicts".
What is it doing today?
Despite the death of Pope John Paul II in 2005 and the resignation of Pope Benedict XVI in 2013, with each having been strong supporters of Opus Dei, the group remains a powerful body within the Catholic Church under Pope Francis, a former Jesuit.
The organisation runs or is affiliated with a large number of schools, universities, training centres and hospitals across the world, and has members in more than 90 countries.
