The McCanns were favourites to win the contest organised by the resort's aerobics teacher Najova Chekaya. After all, the two doctors had brains on their side. Around their table were seven friends from England, three of them also doctors and one a top medical research fellow.

The group of nine were holidaying in Portugal and wanted to have a good time. As one of the doctors, Matthew Oldfield, was to recall: "We drank. So what! We were on holiday."
 

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Madeleine: Questions about her disappearance are growing

But 50 yards away on the other side of the swimming pool, the group's children were sleeping alone. In the bedroom of one ground floor apartment was Madeleine, the McCanns' three-year-old daughter.

Her twin brother and sister, Sean and Amelie, two, lay in cots either side of her. They had been tucked up at 7pm. Half an hour later the McCanns had joined their friends for dinner at the tapas bar.

What happened next has mystified the world.

At 10pm Kate McCann got up from the table to check on her children. She slipped in through the patio windows to find the twins safely asleep - and her daughter's bed empty.

In tears and calling out Madeleine's name, she ran back to her friends to tell them: "They've taken her, they've taken her."

Madeleine has not been seen in the 100 days since May 3. Last night Portuguese police said they were concentrating on what they call the "missing hour" before Mrs McCann found her daughter gone. They say it is possible that she was kidnapped after her father last checked her at 9.05pm and her mother's terrible discovery.

Meanwhile the campaign to keep the public aware of Madeleine's name goes on. It has involved her Roman Catholic parents visiting the Pope.
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Staying on: Gerry and Kate McCann in Praia da Luz

And, on the instructions of JK Rowling, posters of Madeleine were distributed at British bookshops as they opened for the sale of the new Harry Potter book.

This week the donations from the public to a Madeleine fund, financing the PR campaign and global search for the little girl from Rothley in Leicestershire, was nudging £1 million.

More than 50 million people visited the Find Madeleine website in the 48 hours after its launch.

Nothing like this has ever been seen before, and probably never will again.

The campaign has been organised by the McCanns, both 38. Today they believe their daughter is still alive and was abducted by a stranger. Whether the motive was paedophilia, the sale of Madeleine for adoption or even the trade of her organs, they have no idea. Nor do they speculate.

As Mr McCann wrote on his website the other day: "The Portuguese police have assured us on numerous occasions that they are looking for Madeleine and not a corpse."

Yet this week attitudes towards the McCanns underwent a seismic shift, the questions growing more aggressive by the day. The scenario of a small girl being kidnapped without warning on a spring holiday in a family friendly resort is now the subject of lurid debate - particularly in Portugal.

Disturbing questions are being asked about the behaviour of the McCanns and their friends.

The catalyst was the discovery this week, by British police with sniffer dogs, of specks of blood on a wall in the family's apartment.

The blood is now being analysed in this country, raising unpalatable speculation that Madeleine was killed where she slept and was then carried off to the beach or bundled into a car boot.

The reluctance of Gerry and Kate McCann or their friends to speak publicly, or in any detail, about the minutiae of the evening has fuelled the controversy, although they insist it is illegal in Portugal to comment on any police investigation.

In another uncomfortable development the Portuguese press, including the respected newspaper Dairio de Noticias, has claimed that interviews given by the McCann group to police contain discrepancies. Their stories and the timings of their movements on the night do not tally.

Furthermore, emails and phone messages sent between the group - and intercepted by the PolÌcia Judiciaria and British detectives helping the inquiry - are reported to contain conversations that contradict earlier statements.

But the spotlight is equally falling on the seemingly woeful response of the Policia Judiciaria. They only arrived two hours after the alarm was raised. A British expert on child abduction who visited the resort a few days later said it the worst preserved crime scene he had ever witnessed.

Twenty people - including resort workers and other holidaymakers - are believed to have entered the McCanns' apartment after the disappearance. The patio windows at the rear, and the closest point to the tapas bar, were touched by searchers.

The patio had been left open by the McCanns in case of fire and, it appears, so that they could easily check the children.

But what of Madeleine's bedroom? It was situated next to the apartment's front door which is around the corner and a further 30 yards on, next to a road into the resort and a busy carpark.

Notably the bedroom, completely out of the sight of the tapas bar, had heavy, metal window shutters. These were also contaminated in the search.

Even her bedtime toy Cuddle Cat - which is now carried by Mrs McCann - was not isolated for forensic analysis.

Local newspapers and television have criticised the McCann group, who left their children alone for two and a half hours as they wined and dined.

One question being asked is why didn't the parents put their children in the evening creche which is open until 11.30pm? Why didn't they hire a babysitter, bookable at the Mark Warner reception desk?

In a further twist, locals now claim that Madeleine did not always settle well. One evening they allege she ran away into the paths between the apartments, hiding for half an hour when it was time for bed.

Whatever the truth, to begin to unravel the mystery one has to go back to the seemingly carefree days at the start of the holiday.

Gerry and Kate McCann and their friends are like-minded people, with children of similar ages. And they knew each other in the Midlands. Mr McCann is a consultant cardiologist at a Leicester's Glenfield Hospital and his wife is a GP.

Until recently Dr Oldfield worked at Leicester general hospital. David Payne is a senior research fellow in cardiovascular sciences at Leicester University and his wife, Fiona, is a doctor. Another of the holidaymakers, Dr Russell O'Brien, also worked at Leicester University before moving this summer.

Recently they all went to Mark Warner's in Greece where they had devised a plan of leaving their children to sleep while they had dinner nearby.

As Mr McCann explained: "The distance is so small, it was so close it was almost like having dinner in your garden. What we were doing was rigorous with multiple people checking at regular intervals."

When asked if Madeleine might have wandered out through the unlocked patio windows towards the swimming pool, or beyond to the beach, the McCanns dismiss it out of hand.

"We're absolutely certain. We double and treble-checked and have no doubt she was taken," said Mr McCann. Yet another scenario is now emerging in the local press. It is built on the recollections of other guests and workers at the resort.

The official story from the McCanns is this. Mr McCann said he checked on his three children at 9.05pm. He noticed that a door in the apartment which had been left shut was ajar.

He thought nothing of it but it may have indicated that a kidnapper was already there. But his daughter was fast asleep so he went back to the tapas bar.

Another of the group, Jane Tanner, says she took her turn 10 minutes later. She claimed later to police that she saw a dark-haired man of about 35 carrying a child as she walked back to the bar afterwards but thought nothing of it.

Soon after her return - at 9.45pm - Dr Oldfield did his round of the bedrooms. In a first statement to police, it is unclear if he actually went inside the McCann flat.

Indeed, one scenario is that many of the checks of the children were not visible, but involved listening at doors or even from outside the apartments.

However, in a second statement Dr Oldfield insists he did look in Madeleine's bedroom, believes he saw her there, and that there was light coming in through the windows as though the heavy shutters had been opened.

Again, he thought little of it until afterwards. Then, of course, it was Mrs McCann's turn. She found Madeleine gone.

Madeleine's aunt Trish Cameron recalled that she received a call later that night from her younger brother, Mr McCann, who told her: "I went back to check the children at nine o'clock. They were all sound asleep, windows shut, shutters shut."

Mrs Cameron related that when Mrs McCann went to the two apartment a little under an hour later: "The shutters had been jemmied open. They think someone must have come in the window and gone out of the front door with Madeleine."

But what is now perturbing Portuguese police is how could she be abducted when the McCann group were checking so often? Or have reports inadvertently exaggerated how vigilant the parents really were?

A worker at the tapas bar says that only a tall man, believed to be Russell O'Brien, got up from the table during the entire evening. Of course, this witness might be wrong. A busy barman could not have eyes on the McCann party for two and a half hours.

And what of Najova Chekaya, the aerobics teacher running the quiz? She was invited over to the McCann table by Mr McCann himself when the game ended at 9.30. She stayed for half an hour. She later claimed to friends that nobody left the table.

There is another conundrum too. It concerns the sighting by Jane Tanner of the man carrying a child. He was wearing beige trousers and smart black shoes. Her report is taken seriously by police.

Yet a British holidaymaker, Jeremy Wilkins, has given a deposition that does not support her evidence. He knew Mr McCann because he played tennis with him, and was walking his eight-month-old son in the night air when the drama unfolded.

He says that he met Mr McCann, who had come out of his apartment at 9.05pm, and had a word with him. Soon after that Jane Tanner would have crossed paths with Mr Wilkins and his baby.

Mr Wilkins says he saw no man carrying a child or Jane Tanner herself. "It was a very narrow path and I think it would have been almost impossible for anyone to walk by without me noticing," he said.

So today the questions remain. Was Madeleine kidnapped or killed? Or unwatched, did she simply walk out and get lost? How could there be a break in with a jemmy through metal shutters without waking the twins or alerting a passerby?

Someone, somewhere must know the answers.