It is one of the most disturbing and enduring mysteries at the heart of an organization shrouded in secrecy and plagued with allegations of abuse.

To ask about it is to risk the wrath of David Miscavige, 57, Chairman of the Board (COB) and head of the Church of Scientology.

But still the question presses. What has become of his wife, Shelly Miscavige?

Shelly was last seen in public when she attended the memorial service for her father, 'Barney' Barnett in August 2007. Those who saw her described her as gaunt, silent and shadowed by a church 'escort.'

Mike Rinder - the former Scientology spokesman now co-host of Leah Remini's Emmy Award winning show exposing the church - reported recently that an armed security detail had been hired to guard Shelly Miscavige at the church's remote compound at Lake Arrowhead, California.

Writing on his blog, Rinder stated that Robert MacLean - a man known nationally as a TSA whistleblower - had told friends that he was hired to guard Shelly. MacLean would not confirm Rinder's claim.

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Shelly Miscavige, pictured with husband and Scientology leader David Miscavige, disappeared from the public eye a decade ago

On the tenth anniversary of Shelly's 'disappearance' former Scientology 'royalty', Janis Grady, 61, who has known Shelly (pictured left at age 11 or 12) since childhood, lifts the lid on her the now-recluse's dysfunctional past

Now on the tenth anniversary of Shelly's 'disappearance' former Scientology 'royalty', Janis Grady, 61, who knew Shelly since childhood, has spoken exclusively to DailyMailTV.

In a unique insight into Shelly's life and character, Janis, author of the new book Commodore's Messenger which tells of her service to church founder L. Ron Hubbar, has painted Shelly as a miserable misfit, deeply affected by her dysfunctional childhood, who relished the status her role as the COB's wife and assistant afforded her.

And she has shared her own disturbing claim that 56-year-old Shelly is trapped in 'her own personal hell.'

Janis said: 'Shelly came to the ship (L Ron Hubbard's Apollo) around 1972 when she would have been around 11 or 12 years old.'

Janis had known of Shelly's existence because her older sister, Clarisse, and mother Flo, had roomed with the Gilham family when they lived in England and studied with L Ron Hubbard at St Hill Manor, East Grinstead.

Clarisse, Janis observed, did not have a close relationship with her mother, nor, it transpired did her younger sister Michelle, know by all as Shelly.

She said: 'A friend who knew them both in LA before they came to the ship said she never saw any sign of their mother. She described them as these two girls clutching each other and always hanging out together but there was never a parent around.'

Neither of Shelly's parents joined the Sea Org but they let both of their daughters sign up at an early age.

Shelly became shunned by many of her Scientology peers (mostly teenage girls) because she was a 'moody' and 'jealous' and bragged about dating Miscavige (Pictured on her wedding to David in 1982 - right is her older sister Clarisse)

Shelly became 'utterly devoted' to David and L Ron Hubbard but was not well-liked among the other girls (David and Shelly pictured on their wedding day - the two began dating around 1978)

From the get go Shelly was utterly devoted to Hubbard, Janis recalled, but socially awkward and shunned by the rest of his Commodore Messengers - all teenage girls.

She said: 'Shelly was not one to step out of line. She was always kind of in the background. She was very loyal to Hubbard but she was not one that you could say, "Take this project and run with it," because she wasn't experienced enough or had enough street smarts about her to make her own decisions.'

Shelly was not, Janis said, well educated: 'She probably went to fifth grade maybe and that was it because when she came to the ship we didn't have school.

'We had three hours of reading and writing and arithmetic but that doesn't teach you critical thinking. And she was a loner.'

Shelly gained a reputation among the other girls for being moody and for taking so long over her hair, make-up and outfits that often, when the rest of the messengers were going ashore on a 'liberty' (leaving the ship) they would simply leave her behind.

Years later, Janis said: 'I remember her bringing up to me how she did not like me back on the ship because I would go on liberty without her.'

Looking back she admitted: 'Shelly was a lot younger than the rest of us so she did have that disadvantage. But she didn't have a very good relationship with the core messengers.'

Janis met Shelly aboard The Apollo, the flagship of L Ron Hubbard's Sea Org fleet, when the two were teenage girls

Janis left the church in August 1990, but served as one of Hubbard's original Commodore Messengers aboard the Apollo

Certainly, when Shelly set her sights on snagging David Miscavige there was no love lost between her and any potential rivals.

Janis said: 'There was a group of younger girls and there was not a big selection of guys. The two best guys were probably Dave [Miscavige] and Marc Yager (who went onto become one of the church's most senior executives). One was short, one was tall, but there wasn't a big selection of guys and I remember a bunch of the girls competing to get Dave.

'And when Shelly finally got him her attitude towards the other girls [about everything] was very much, "Well you're just upset because I got Dave."

'So that of course doesn't go over well with the other girls - they moved on and married other guys and were happy, but she would bring that up.

'She was moody, she was a jealous type of person.'

When disgruntled, Janis said, Shelly would simply not talk to a person, sometimes giving them the silent treatment for days on end.

Miscavige was, Janis recalled, far more personable and outgoing than Shelly when the pair started dating around 1978.

L Ron Hubbard is seen giving bride Terri Gillham (Janis's sister) away on her wedding day in 1974, as Shelly stands behind her holding her veil

Janis (pictured in a blue dress) recalls Miscavige as being good company, but Shelly (pictured in pink) was always aloof

By then they were at Scientology's International or Gold Base - a secure compound set in scrubby ranchland about 90 miles east of Los Angeles.

Janis's husband, Paul, worked with Miscavige and got along with him so well that, when he and Janis married they asked Miscavige - who once worked on the church's educational and promotional movies - to be their photographer.

The couples vacationed together, skiing at Big Bear and lodging first in a cabin and later in condominiums bought by the church.

But while Janis recalled Miscavige as being good company, Shelly was always aloof.

Others who knew the couple have stated that they never once saw Miscavige or Shelly kiss, touch or hug each other in all their years of marriage.

Janis said: 'Like everybody they had their ups and downs, but you definitely knew that it was Dave who wore the pants in the family.

'Shelly listened to what Dave had to say.'

But, however apparently cool the relationship was, at least publicly, it was one from which Shelly benefited at first as Miscavige rose to power.

According to Janis: 'Shelly definitely had ambitions for Dave. She was very supportive of everything Dave did and I don't know if she knew this but we called her "Queen Bee," because she turned her nose up (at us all).'

Janis knew Shelly because her older sister, Clarisse (pictured on top of Janis on the top of the pyramid) and mother Flo, had roomed with the Gilham family when they lived in England and studied with L Ron Hubbard at St Hill Manor, East Grinstead

Shelly was by his side, Janis said, as Miscavige became increasingly vindictive to members who crossed him.

She supported him as he dished out punishments and sent people to the Rehabilitation Task Force - a secure place where members branded 'suppressive' were forced to wear black boiler suits, berth in dormitories, eat rice and beans, run everywhere and do the most menial labor.

When she was employed as his assistant she basked in the job of being the 'enforcer' of his orders.

Janis said: 'Shelly was very rote. Dave would do things and she would chase up his orders and this would just drive everybody nuts.

'She would take her notes and it was her job to make sure she got compliance to those orders.

'She set up a system hat would just send out to us these automatic nudges and here you are trying to manage internationally and handle different things, or keep an affluence going or keep an expansion going and it's like you've got this bee that keeps coming and stinging you and won't leave you alone.

Miscavige, who went on to be the leader of the church, is said to be the one 'who wore the pants' in the relationship

Miscavige (bottom left) pictured at another Scientologist's wedding

'That's how she was. But you're not going to tell the COB, "Your wife's driving me nuts."

But while Shelly's status rendered her pretty much 'untouchable' it also left her isolated and therefore vulnerable.

Janis left the church in August 1990 so, she said, everything that she knows of Shelly after that point has come to her through fellow ex-members who stayed on longer.

One anecdote told by the former church spokesman, Mike Rinder, relates how, when he saw her in 2006 - at which time Miscavige was in Los Angeles while his wife remained on the base - Shelly asked whether her husband was wearing his platinum wedding ring or his gold one.

His observation was that it was 'like she didn't want to ask me if he was still wearing his wedding ring.'

Many have pointed to the possibility that Shelly fell foul of her husband when, during his sojourn in Los Angeles in 2006, she took it upon herself to undertake a task already attempted by various Sea Org members who had failed to satisfy Miscavige with their efforts.

Miscavige wanted a new improved 'Org Board' but had rejected every suggestion submitted for the corporate shake up.

Notorious defector and former friend of Shelly, actress Leah Remini has claimed that when she asked about her absence from public life at Tom Cruise and Katie Holme's wedding she received a torrent of abuse and harassment

While he was in Los Angeles Shelly came up with her own plan and informed everybody of his or her new title and duties. She also started plans to renovate Miscavige's living quarters and had some of his things boxed up and moved to a temporary housing unit.

Janis does not know if this was the catalyst for whatever happened to Shelly.

'Shelly's whereabouts have never been publicly confirmed by anyone within the church of Scientology.

Janis Grady's new book Commodore's Messenger: A Child Adrift in the Scientology Sea Org,' by Janis Gilham Grady is out now

Notorious defector and former friend of Shelly, actress Leah Remini has claimed that when she asked about her absence from public life at Tom Cruise and Katie Holme's wedding she received a torrent of abuse and harassment.

The actress filed a missing person's report on Shelly in 2015 but San Bernardino police stated that they had spoken with Shelly and dropped further inquiries.

But Janis is doubtful that this is a reassurance that Shelly is safe and well, saying: 'I have no doubt they spoke to Shelly but there was probably somebody standing beside her when they did.'

According to Janis, another former Scientologist saw communications addressed to Shelly at the religion's notoriously secret and secure base near Lake Arrowhead, California back in 2006.

Janis said: 'For the Scientology spokesman to say that she's happy or she's on project…that's not Shelly.

'Because Shelly liked her freedom. She liked dressing up. She did like going to events and things like that.

'She was the Queen Bee and to have that all cut from her along with her husband and not go to any of the socializing she was getting, she was enjoying…she liked the attention as his assistant and his wife. She liked that.'

Whatever the truth regarding the state of her marriage, Janis said that it was inconceivable that the head of the church of Scientology would divorce.

She explained: 'Hubbard has written policies on how to do marriage counseling to avoid a divorce. So if the counseling actions have been done they should be back together as a happy couple.'

Janis added: 'If she [Shelly] came banging at my door I'd let her in. What's past is past. I'm not happy that she's in the situation she's in. I wouldn't wish that on anybody.

'She didn't have a great childhood and she is not leading the life that she was. She is not with her husband. I would have to say she's probably not physically mistreated but she's in her own sort of hell.'

In response to a comment request by DailyMail.com, a Scientology spokesperson commented: These allegations are false and are part of a pattern of harassment against the Scientology religion and its leader.'

Janis Grady has not been a member of the Church of Scientology for nearly 30 years. We have not read her book, but the false allegations you raise are contrary to our records about the early days of the Sea Organization

'Commodore's Messenger: A Child Adrift in the Scientology Sea Org,' by Janis Gilham Grady is out now