Officers were tipped off by the parents of Zachary Nicodemous, a usually timid, well-behaved teenager who announced one day that he was leaving their Essex home to become a full-time "apprentice" in the Kaotian cult. Zachary - a Star Trek fan whose previous ambition was to be a computer technician - is now hiding out in the pebble-dashed lair of Lee Thompson, self-styled "master of the Darlington Kaotians".

Kaotians, for the benefit of the uninitiated, are an offshoot of the Goreans - a cult with about 25,000 members in Britain. (Amazing: who knew?) Both groups are inspired by the Chronicles of Gor, a series of sci-fi fantasy novels by John Norman, the pen name of Dr John Lange, a philosophy lecturer from New York.First published in the 1960s, they are politically incorrect beyond the wildest dreams of The Daily Mail.

On the planet Gor, where insectoid priest-kings rule, species are divided into strict castes and there is no pretence of equality between the sexes. Instead, men and women strive to attain the perfect master-slave dynamic. Gorean men are muscular and merciless, their women soft as butter. Most are slave-girls, or kajira, who grovellingly submit to their master's sexual commands, as well as cooking, cleaning, and servicing the master's friends where necessary. A typical passage, from the 1978 classic Beasts of Gor, gives a flavour of the genre:

"It is late now," I said. "I think we should sleep."

"What is your name?" he asked.

"Tarl," said I. "Let that suffice."

"Accepted," he said, smiling. He would not pry further into my affairs. Doubtless he assumed I was bandit, fugitive or assassin.

I took Constance by the arm, and threw her to his feet. It was a simple act of Gorean courtesy.

Constance looked at me, wildly. "Please him," I said.

"Yes, Master," she whispered.

The trouble is, this kind of caper doesn't go down so well in Darlington. The neighbours already had reservations about Lee Thompson - a plump man in his early thirties with a carefully cultivated look of diabolism (shaven head, goatee beard, fiendish smile playing about the lips). The local butcher banned him from the premises after he turned up with his girlfriend on a leash.

As for Zachary's parents: they are worried sick. "He told his mum he had met the master of the Kaotians on the internet and had decided to join his cult," said a family friend. "It has made her hair stand on end because he is not exactly a man of the world. He had never even had a girlfriend."

Alas, these should have been the warning signs. Fantasy sci-fi has always been the particular vice of the nerdy, withdrawn teenage boy. Filled with manly desires but trapped in the body of an acne-ravaged half-child, longing to seduce the girl of his dreams but lacking the courage or the know-how - can he be blamed for preferring fantasy to reality?

In my day, boys of Zachary's ilk sought solace in Dungeons and Dragons. It was always a wonder to me, how much pleasure these gentle, bespectacled creatures could derive from slaying gnolls or doing battle in the troglodyte cavern. Generally speaking, the more knock-kneed and pusillanimous the player, the more ferocious-sounding his chosen character would be: Blade, Warrior of the Giant Kings, or some such.

The recurring themes of fantasy fiction - master races, mighty battles, baffling Elvish vocabulary - are all evident in The Chronicles of Gor. Crucially, so is the one thing that Dungeons and Dragons lacked: sex. Dr Langan, perhaps sensing that his typical reader wouldn't have much luck with the ladies, created an imaginary race of women who never say no. With the advent of the internet, it was only a matter of time before a cult was born.

Living one's life according to the rules of fantasy fiction is, however, a trickier proposition than just playing at goblin warfare after school. There is, for instance, the dispiriting contrast between ruling over the vast plains and mountains of Gor, and ruling over a pebble-dashed terrace in north-west England. On Gor, the bravest warriors get to fly about on enormous prehistoric birds; in Darlington, it's just trains, trains, trains.

And then there's the problem of the natives. Lee Thompson claims there is no shortage of volunteers to be Kaotian slave girls. "It is all voluntary and safe. Lots of women want to come and find out about it." Reading between the lines, however, it seems that not all are impressed with what they find. "It's hard work for everyone," sighs Thompson. "Girls leave when they've had enough."

I don't think it's the hard work that puts them off: it's the gradual realisation that their "masters" are in fact overgrown nerds. It's one thing to be submissive: quite another to have to do it in Elvish.

jemima.lewis@virgin.net