The Panacea Society appears relatively harmless when it comes to bizarre cults.
Based on the writings of an 18th century prophetess - Joanna Southcott - the society's members have some very specific yet strange beliefs.
The central tenet of their faith is that when the Messiah returns for the Second Coming, he will make his grand entrance in Bedford.
Given that they own several houses around the town, which are let out to members of the eccentric group, cynics could argue that they're simply trying to push up property values.
It could be the ultimate 'des res' - an end-terrace next door to Jesus Christ!
They are so confident in their belief, they have even bought a house and done it up especially for him at 18 Albany Street in the town, the alleged original Garden of Eden.
Tonight, for the first time cameras get a peek inside the prospective House of God, where the current tenants are on two months notice.
You have to wonder whether Christ will have time to let them know a couple of months in advance of his arrival, what with arranging the Second Coming and rebuilding the new world around Bedford.
Members even seriously discussed whether a shower unit should be installed or not!
The Panacea Society, which is believed to be worth around (pounds) 30million thanks to their prudent property acquisitions, come across as being weird, but less sinister than other cult religions.
The society flourished between the two world wars, and has traditionally been a very secretive organisation. As with many of their counterparts, they were convinced that the Apocalypse was nigh as the Millennium approached.
Over a 22-year period, Joanna Southcott wrote a total of 65 books, in which she relayed the word of God as revealed to her through 'divine messages'.
Certain of those books she was allegedly instructed by God himself not to publish, but to lock up in a box or ark, hence the ark of the documentary's title.
She stated that the box could only be opened before a gathering of 24 bishops of the Church of England, divulging the secret to ending crime and distress.
The Church's response in the documentary is predictably scathing.
Just before her death in 1814, Southcott proclaimed that she was to give birth to a child by immaculate conception, who would be named Shiloh. The pregnancy never materialised, she died childless, and doctors said the cause was cancer.
A tale, which has persisted for nearly 200 years, is now unravelled in this fascinating documentary narrated by Alison Steadman.