A grim, soulless place where a dusty sea-wind whistles constantly through the narrow streets and the darkened bazaars seeth with intrigue, the Moroccan town of Fnideq is Africa's last settlement.

Just around the headland of its northern tip, beyond a chaotic, badly-policed frontier, stands Ceuta, the Spanish-owned equivalent of Gibraltar. And across the shimmering straits, so close that the houses are clearly visible, lies the jagged coastline of Europe, an El Dorado for the great many shadowy types who pass this way.

 

Tragically, the sight of a cute-looking child clinging forlornly to some strange adult hand is no great rarity here.

In a land where small boys and girls are routinely sold as house-servants and sexual playthings, a wretched infant cargo moves stealthily from one continent to the next without attracting so much as a second glance.

 

Last month, however, by grace of her blonde hair, apple cheeks and a milky complexion, one little girl looked so strikingly different as she was swept along Fnideq's teeming streets in the clutches of a middle-aged Arab woman that someone finally took notice.

 

The curious onlooker was a 24-year-old Moroccan woman named Naoual Malhi, and - improbable as it may seem - her sharp observation and quick wits may yet provide the key to the most compelling mystery in living memory: what happened to Madeleine McCann?

 

Although Morocco stands so close to Spain and Portugal, few people here have heard of the four-year-old English girl who vanished from a holiday apartment six months ago.

The case is mentioned in newspapers and on TV from time to time, but, fearful of upsetting King Mohamed VI and his puppet government, editors refrain from mentioning the most enduring theory: that Madeleine is being held captive by paedophiles in Morocco.

Moreover, two-thirds of the population are illiterate, and most people are too busy ekeing out a meagre living to take more than a passing interest in world events.

Mrs Malhi is different, however. A much Westernised Moroccan who wears fashionable clothes and lives in an expat British community on the Costa del Sol with her own four-year-old daughter, Ines, she has avidly followed the saga unfolding in Portugal's Praia Da Luz, five hours' drive away along the Iberian Peninsula.

 

And because posters bearing Madeleine's face are pinned up everywhere in the shopping mall near her apartment in Calahonda, near Malaga, she is familiar with Madeleine's distinguishing features.

Of course, Naoual Malhi, a divorcee, may turn out to be one more unsound witness. Or she could simply be mistaken in what she saw. However, she does not appear to be a crank.

 

Plausible and unexcitable, she is a qualified doctor and says she hails from a well-to-do family from Fez, Morocco's religious and cultural capital. She has asked for no money in return for her information, and much of it has been verified.

It was in late September, at the end of a fortnight's holiday in Morocco, that Naoual first spotted the girl she now refers to unequivocally as "Madeleine" near Fnideq's outdoor market.

 

Though people with fair hair and light skin colouring are not uncommon in Morocco, Naoual was struck by the incongruous sight of a Berber woman, wearing traditional Arabic clothes, carrying a beautiful, blue-eyed, "very blonde" girl, dressed in jeans and an orange jumper.

 

In an exclusive interview with the Daily Mail this week, Naoual described what happened after she drew up closer behind them.

 

"The woman spotted me looking at them and tried to hide the girl and shield her face," she said. "But I knew, the minute I saw her close up, that it was Madeleine.

 

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"I'd seen her picture a thousand times, and the girl I saw was her. She had that distinctive right eye where the pupil runs into the iris.

 

"She was exactly the same as in the pictures, except that she had a bump like a bruise on the left side of her forehead and her hair was a lot shorter, like a boy's."

 

Naoual paused, then added solemnly: "It is like me seeing my mother and knowing it is her."

This remark was clearly meant to set the seal on her story, for Moroccans do not make reference to their parents lightly.

She followed the pair to a taxi rank. When the woman hailed one of the dozens of rusting, six-seater Mercedes taxis in Fnideq, Naoual tried to climb in as well, for it is commonplace there for strangers to share cabs. Perhaps tellingly, however, the woman refused to allow her to ride along.

Naoual, though, had the presence of mind to get the driver's phone number. She later called him to discover where he had driven the pair, then alerted the Spanish police.

 

They came to see Naoual, and on October 6 she was contacted by Metodo 3, the Spanish private detective agency hired at great expense by the McCanns to trace Madeleine - or at least discover what happened to her.

 

Since she vanished, many people have come forward to report seeing her, and at least four of these "sightings" have been in Morocco. The most recent turned out to be the fair-skinned, blonde-haired daughter of a Berber farmer who bore a passing similarity to Madeleine.

 

But Metodo's seasoned investigators did not lightly dismiss Naoual's story. They were excited to have found someone who claimed to have seen the now-famous "flash" in Madeleine's iris. After interviewing her at length, they asked her to return with them to Morocco.

 

So, earlier this month, Naoual quietly slipped back to her home country with a Metodo team led by Antonio Jimenez, the former head of Spain's national organised crime squad. They spent a week trying to track down Madeleine.

 

Plainly, this latest operation has not found her. At least, not yet. The question is, did Naoual really stare into the most instantly recognisable eye in the world?

 

This week, armed with information she furnished to the private detectives, plus other intriguing leads that have emerged since - and a photograph of Madeleine - I travelled more than 700 miles through Morocco in an effort to uncover the truth behind her story.

Naoual and the Metodo investigators began their search with a 25-minute hydrofoil crossing from Tarifa, Spain, to Tangier. A one-way ticket costs a little over ?20.

 

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This week, I also took this route to Morocco. On the wall at the ferry port, a familiar, dog-earred picture, overshadowed by a huge Wanted poster bearing the mugshots of six suspected ETA terrorists, urges anyone with information about Madeleine to call Crimestoppers. It's written in English.

 

Once in Morocco, Naoual phoned the taxi driver, Mohamed, who told her he had driven the woman and child from Fnideq to Al Hoceima, a former Spanish garrison town nestling further east along the Mediterranean coast.

 

If true, it was an unusual and expensive journey. The 200-mile trip would have taken five hours over tortuous mountain roads, and the fare would have been around ?180: a month's salary for many Moroccan workers.

 

"Our drivers take people to Al Hoceima maybe once a month," the taxi controller at Fnideq told me. "They always share a car because it is so expensive."

 

Questioned further by Naoual, the driver said he dropped "Madeleine2 and the woman at a taxi rank in the town. "He told me the girl was crying throughout the journey and didn't speak Arabic," says Naoual. "He didn't know what language she spoke in.

 

"The woman didn't say much and didn't try to comfort the girl. She told the driver she was the daughter of her sister, who lived in France."

 

The driver, Naoual says, refused to meet her and provide more details. Fearful of upsetting the authorities by speaking out of turn, he didn't want to get involved any further.

 

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As I discovered, this is the sort of attitude that is hampering Metodo's inquiries in Morocco. Apathy and the culture of bribery cause further problems; it is remarkable how many people suddenly recognise Madeleine's photograph when they scent a wad of dirham banknotes.

 

Then there is the problem of national pride. Among the many ordinary Moroccans I spoke to this week, not one was willing to accept that paedophilia exists in their country. This flies in the face of a recent UN report which stated that child brothels and sex rings operate in most of Morocco's major cities.

Three years ago 26 people were arrested when a wide-reaching paedophile network was uncovered, and last August Irishman Christopher Croft, 66, was jailed for 12 months for drugging and abusing a teenage boy.

 

Before being sent to prison, Croft lived in Taghazout, a small fishing village near Agadir which is said to have been virtually colonised by an international group of paedophiles. According to informed sources, the group routinely abuse children as young as seven with impunity, bribing local police to turn a blind eye.

 

King Mohamed's ministers will doubtless point to recently-introduced tougher sentences for child sex offenders as proof that they are taking the problem seriously. Yet at a time when foreign investment and European tourists are pouring in as never before, there remains a tendency to deny there is a problem at all.

 

This week, when the Mail asked a senior government minister to comment on reports that Madeleine is being held by perverts in Morocco, he warned that we could be in serious trouble simply for investigating this scandalous proposition.

 

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The international child protection organisation Don't Touch Our Children dismissed a report that Madeleine might be being forced to work as a petit bonne, or "little maid" - the old French colonial term for the hundreds of children held against their parents' will and put to work as house slaves by wealthy Moroccan families.

 

"It's nonsense," said director Amal Merimi. "We don't have any cases of abuse [of children] that age. Normally the maids are 12 or 13 years old."

 

So if Madeleine really was in the taxi a month ago, what became of her after being taken to Al Hoceima?

 

Naoual and Antonio Jimenez drove to Fez, 300 miles south-west of Al Hoceima, to request assistance from a local police chief, a family friend.

 

Staggeringly, the high-ranking officer knew nothing about Madeleine, and so gazed blankly at her photograph. However, when they explained that she was missing, he agreed to help - though not officially. And for a fee, naturally.

 

The officer enlisted lower ranking policemen in outlying stations, who, in turn, sent a small army of young boys to show the picture to people in the dozens of small towns and villages surrounding Fez, in the starkly beautiful Rif Mountains. Anyone who recognised Madeleine was asked to call Naoual's mobile.

"We got hundreds of calls that week," she recalled. "About 200 of them said they had spotted a girl with a woman aged around 40 wearing a chilaba headscarf.

 

"Sometimes they also said there had been a teenage girl aged between 14 and 16 with them. They thought she, too, was a Berber and looked like the woman's daughter.

 

"The sightings were all over the north of Morocco, mostly in the area of the Rif Mountains. Some agreed to see us, but others just gave the information and hung up. There was one person - a lawyer - who started asking for money straight away. He said he could help us but wanted 3,000 euros. We said no.

"Then there was a storeholder on the contraband market in Fnideq. He said he had seen the girl with the woman when she came to buy cheese and milk from his stall. He said he gave the girl a lollipop and noticed her distinctive right eye."

 

Another elderly couple placed "Madeleine" in Meknes, a northern city. They had been at a funfair with their grandchildren, and claimed to have seen the little girl crying as she dismounted from a train ride. They offered her a sweet, but she replied "No" in English. Then the woman she was with ran over, grabbed her hand and pulled her away.

 

Were all these callers simply spinning stories in the hope of a reward? Had they merely seen another Madeleine lookalike? Or had they really spotted her?

 

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For the detectives, working in a country three times the size of Britain, with poor communications, even checking out one of these leads was a painfully slow process, and eventually Naoual returned to Spain.

 

Still believing Madeleine is being held in Morocco, however, the Metodo team have remained behind, and a few days ago, Jiminez called Naoual again. He asked her to phone someone who had contacted him but spoke only Arabic, a language he does not understand.

 

This caller turned out to be rather different from the rest: an articulate schools inspector from a sprawling but remote mountain village of some 15,000 people, not far from Fez.

 

He said he was sitting with about 15 neighbours, and they all had the same story to tell. They had studied the circulating photograph of Madeleine carefully, and felt sure that this was the strange new girl they had seen in the village recently. She lived on the outskirts of the community with a Berber woman, aged around 40, and a teenage girl, aged around 15.

 

Listening to the man, Naoual's pulse quickened. Everything seemed to tally.

 

Naoual says she passed the new information to Jiminez, but she is not sure whether he found time to go to the village because, a couple of days later, he was back in Spain. She also informed the police in Fez, who have done nothing.

So I followed the trail through the mountains to the village. Its people are mainly poor farmers and small traders. The village is too poor to have its own police station, which would obviously have advantages for anyone hiding an abducted child.

 

But when I spoke to the schools inspector who had alerted Naoual, he remained convinced that the little girl in the photo and the child who lives near the village are one and the same. Currently visiting relatives 400 miles away, he is returning home soon and is confident he can prove what he says.

 

Naoual, for her part, believes Madeleine is languishing somewhere in the country of her birth.

 

"I know some people will think it sounds fantastic when you start talking about little European blonde girls being kidnapped, taken to Morocco and sold," she says. "But I am Moroccan and I think it is totally feasible.

 

"It's a very secretive country and there are a lot of girls who are stolen and held in cellars, to be sold for sex.

"I don't want a penny for my story. All I want is for Madeleine to be found safe and well, and reunited with her parents. She is in Morocco. I'm sure of it."

 

Tonight, near their Leicester home, Kate and Gerry McCann will be attending a special church service, timed as precisely as possible to mark the moment, six months ago, that Maddie went missing.

 

Meanwhile, my search in the mountains will continue. In my heart, I fear that it will prove fruitless.

 

Wouldn't it be wonderful, though, to find a little blonde English girl with a tell-tale flash in her eye?