It is one of the worst nightmares a family can face - a loved one who disappears into a cult.
This is the scenario facing the family of Lucie Blackman, a 21-year-old Briton working as a hostess in Tokyo, who went missing on 1 July.
Japanese police are investigating whether she was abducted by one of the customers at the late-night members' club where she was paid to chat to drinkers.
After Ms Blackman failed to return, a friend received a phone call from an unknown man, who claimed the former air hostess was joining a "newly-risen religion" - the Japanese term for cult.
Ian Haworth, general secretary of the Cult Information Centre (CIC), says it is a myth that cults target young, unhappy people.
"The most likely candidates fit the following criteria: They come from an economically advantaged background; they are of average to above-average intelligence; well educated; and described as idealistic.
"That's just the opposite of what society would imagine."
Should a loved one - a son or daughter, a parent, a partner - be lured into a cult, friends and family should take it seriously, Mr Haworth says.
"A cult isn't playing games; it's playing for keeps. The aim of the average cult is to recruit for life, or until that person is no longer useful to them."
'Love bombing'
Mind control techniques work very quickly on unsuspecting individuals, he says, warning that it can take just three or four days for a new recruit to be broken down.
In 1978, Mr Haworth was himself rescued from a Canadian cult he had joined two and a half weeks earlier: "It took me 11 months to get over it."
Typical techniques employed by cults include hypnosis, peer group pressure, deprivation of food and drink, and "love bombing" - creating a sense of belonging through constant hugging and flattery.
Leaders may also bombard the new recruit with complex lectures on incomprehensible doctrine, which can break down rational thought, and implant subliminal messages by repeating slogans.
"And while it's happening, it feels good," says Mr Haworth.
People in new towns, unfamiliar with local customs, can be particularly vulnerable.
"Imagine if you are in London and a complete stranger comes up, says 'Hi!' and starts chatting. If you were a Londoner, you'd probably give them a wide berth.
"But if you are fresh off the boat, you might think 'Gosh, Londoners are friendly' and be prepared to listen to them."
Should friends and family suspect a loved one has got involved with a sect, they must avoid going public with their fears.
"If the cult gets wind of any publicity, it can make the member disappear. I don't mean kill them, but it may well have other branches around the country or in other parts of the world."
The CIC recommends refraining from ridiculing the member's beliefs - he or she will have been programmed to regard outsiders with suspicion.
Know your stuff
After re-establishing contact, friends and family can try and deprogram the member themselves, or employ a reputable exit counsellor.
"It has to be in a voluntary session - the member has to agree to counselling, even if they don't think they need it."
Those who choose to do it themselves must exhaustively research the cult, the terms it uses, and its methods so they can talk to the member on the same wavelength.
"Raise questions about the corrupt side of the group - there is always a corrupt side, be it Swiss bank accounts or limousines."
Emphasise the difference between conversion and coercion. If a member begins to realise the powerful experience they went through was man-made, not divine, they may again start to question what they are doing.
Most important of all is to remain patient and constantly express your love and support, Mr Haworth says.
He warns the process could take a week, a month, a year - and in some cases, the member may never leave the cult.