In front of the pretty whitewashed chapel where prayers have been said all week, they gathered in a vigil for Madeleine McCann last night.

They wore or laid items of green ­ plants, trinkets and T-shirts ­ to create a symbol of hope that she will be found. But instead, as Madeleine should be waking for her fourth birthday in a Leicestershire village, the search for her is looking increasingly hopeless. There were new leads in the Portuguese newspapers yesterday, as there have been all week. A man who fled with a blonde woman after photographing young girls, a few days before Madeleine vanished, drove a car with British number plates. They might be the same "British" couple caught on CCTV at a petrol station at Lagos, near Praia da Luz, hours after the abduction. Another couple, possibly British, from the McCanns' holiday complex ­ the Mark Warner Ocean Village ­ were said to have been taken to a nearby police station, perhaps for an identity parade in front of Madeleine's parents.

But neither of the unconfirmed reports really stacks up. Would abductors really stop at the first petrol station just out of the resort? And would suspects stay at Ocean Village, under the noses of police?

So Portugal's Policia Judiciaria (PJ) is abandoning its ground searches for Madeleine and going right back to the beginning. They have reinterviewed Madeleine's parents in a major review of the evidence. But they seem as far away as ever from knowing who spirited Madeleine from her bed as her parents dined amid the whitewashed walls and bougainvillea at a tapas bar, on the other side of the swimming pool, nine days ago.

There is no telling how many clues have been under detectives' eyes all along but Stella Cash is certainly the kind of person who might have provided some. She was working at the Duke of Holland bar, 100 metres from the place where Kate McCann, Madeleine's mother, walked from the bar ­ past the swimming pool, up her apartment's 10 stone steps and through the child gate ­ to look in on her daughter at 10pm.

Several Mark Warner guests dined at Ms Cash's restaurant that night and she later drove home past the McCanns' corner apartment at 10.50pm but no police officer has questioned her about what she saw. "I don't think I saw anything suspicious but then I don't know what they might call 'suspicious'," she said. These are the individuals who form a vital part of an inquiry such as this, according to a serving detective chief superintendent who has put several child killers behind bars. "You start by clearing the ground around your feet," he said. "You need to know who has been in and out of every business near that scene."

Security was precisely what Kate and Gerry McCann, a GP and cardiac consultant, had in mind when they and three other couples with children, all from the medical fraternity, settled for the complex. It was their first holiday of this kind. They booked with a company that has a reputation for creating hermetically sealed, child-friendly English enclaves in the sun. The Ocean Club, set in the one-time sardine fishing village of Praia da Luz, is unlike other Mark Warner sites. It is set within the village and the McCanns' ground floor apartment backs on to a crossroads. Mark Warner makes a virtue of the fact. "You're as likely to meet a local as a tourist," reads the literature.

The McCanns' week was not the warmest but it had passed off well. There were tennis sessions on the two courts, where Madeleine stopped for a picture holding tennis balls, and a visit to nearby Sagres, where the family enjoyed a walk through the streets (Madeleine and her mother hand-in hand).

Mr and Mrs McCann seem to have dined at the tapas bar with their group most nights ­ and this routine was probably a critical factor in their daughter's disappearance between 9.30pm on their penultimate evening in Praia, when her father looked in on her, and 10pm, when her mother found she had gone.

Amid all the rumours surrounding the case, it is hard to resist the assumption that the McCanns' evening routine was being observed and her abduction planned. The abductor forced up the louvre blinds on a rear bedroom window to gain entry to Madeleine's room. To have made that entry to a random apartment would have been risky in the extreme.

Once into the room, a quick escape ­ not through the unlocked front door, in view of Madeleine's parents, but through the window, a short walk out of the drive to a car parked in the adjacent Ruo do Ramalhete ­ was easy. The A22 motorway ­ which cuts across the Algarve ­ is 10 minutes away. At speed, the Spanish border is 90 minutes away. The border might have been sealed in time had the police been alarmed by the distress call from the Ocean Club. Instead, it took a desperate call to GMTV from a McCann family friend, Jill Renwick, to alert the British nation to the inaction.

The British media piled into Praia, so starting one of the defining aspects of this case: the confrontation between a British press corps accustomed to information and a Portuguese police inspector insistent that Portugal's segredo de justica law would prevent him revealing anything to the press or even to the McCanns.

By Tuesday, there were near scuffles at a chaotic press conference as Chief Inspector Olegarion Sousa was encircled by journalists pressing for details. The segredo law has been applied in the extreme, with no attempts by the police to involve the public in the search for Madeleine.

A telephone number for witnesses to call, published on a police website has still not been made public by Mr Sousa. Neither has an e-fit of the suspect, leaving reporters to seek out at least six e-fits which have been in circulation ­ one of which, bizarrely, showed the shape of a suspect's head, with no face.

Mr Sousa waited until Thursday to issue a photograph of the pyjamas Madeleine was wearing, an image the McCanns had made public four days earlier at a press appeal they initiated.

The McCanns have now relocated, with three Leicestershire Police family liaison officers, to an apartment near the one from which Madeleine was snatched.

It is unclear whether they have been digesting the scraps of information reported by the Portuguese papers, watching Mr Sousa's chaotic appearances; or following TV reports about roadblocks from northern Portugal to the Spanish border.

On most days, there has been a statement, an appearance or a new image ­ to ensure momentum is maintained. David Beckham was on board yesterday with a personal appeal. Later, a £1.5m reward was laid down.

But their deepening sense of horror has been palpable in their daily appearances ­ to place their two-year-old twins, Sean and Amelie, in a creche, attend the local church or, as yesterday, to make the declarations of hope.

On Thursday, Mrs McCann was visibly distressed and needed to be supported into church by a friend for a service of hope for her daughter in which the first hymn "Father Hear the Prayer We Offer", offered more succour than a priest could. "Give to the winds thy fears, Hope and be undismayed ... God bears thy sighs, God shall lift up thy head."

Praia da Luz, a village whose population is made up of approximately 50 per cent British expatriates, shares their horror. Many holidaymakers continued an apparently random and futile search for Madeleine yesterday, despite the police decision to call it off. "We're parents. What more can we do?" said one woman. "How can you possibly holiday?" said Maggie Allen, 56, a nurse who arrived on Monday for a two-week holiday and has instead spent her days walking potholed tracks in her sandals.

The posters that locals have issued around bars and restaurants also reflect the random nature of the search when the public, and not police, take control. "Maddie McCann, white PJs, taken last night," reads one. Madeleine never answered to Maddie and her pyjama top was pink.

Does the decision to stop the ground search reflect a disastrous investigation? No, says David Hill, a former area commander of the National Crime Squad and now working for security firm Red 24. "There's nothing alarming about scaling it down," he said. "If they have done the search thoroughly, there's no point going over the same ground. You must scale that side of it down and concentrate your resources."

Professionals such as Mr Hill believe Madeleine was either abducted by a paedophile ring, taken by someone desperate for a child of their own, or by someone looking to sell a child for adoption. "Paedophile ring might sound dreadful but it doesn't necessarily mean something awful will have happened to her," he said. "By continued detective work, she can be reached."

The critical question ­ one Portuguese police seem unlikely to answer ­ is what scientificc evidence has been gathered from the McCanns' apartment. Forensic officers will have used tape to pick up fibres and will be seeking DNA deposits from the abductor's perspiration or saliva.

There might be fingerprints. It is likely that in a case of such high profile that forensic analysis will be complete by now and results checked against Interpol and Europol databases. "Officers should also be tracing and eliminating every Ocean Village resident from the past few weeks and eliminating them," said Mr Hill.

CCTV cameras are few and far between here ­ one at the local supermarket, where one of many possible suspects was seen, is not functioning. But a theory that a British couple who were captured on camera may be under suspicion continued to gather momentum yesterday.

A man who said his daughter and other girls had been photographed by a man with a blonde woman in a Renault Clio with British plates at Sagres, near Praia, insists the same woman was caught on CCTV at a service station near Lagos. That would have been on the A22 to the Spanish border on the night of Madeleine's disappearance.

The couple, reportedly in their 40s, had been staying at an appartment in the Solimar apartments in Borgau, near Praia, where the petrol station CCTV images were being distributed.

After nine days, it doesn't seem much to go on, but Gerry McCann, shaking slightly as he read his statement, only has hope to hold on to. "We will leave no stone unturned in the search for our daughter," he said.

The words of the toddler's parents

"We have now seen at first hand how hard the police are working in the search for Madeleine and their strong desire to find her.

"We have also seen the resources being put into the investigation.

"We are doing absolutely everything to assist the police with their investigation and we will leave no stone unturned in the search for our daughter Madeleine.

"We are very grateful for all the effort and offers of support that we have had from home and around the world.

"We have been moved by the enormous willingness of people to do all they can to help find Madeleine.

"As we have said before, we are positive and focused on the investigation.

Thank you."

So what could have happened? Five possible explanations...

Paedophile ring

The most likely theory, according to experienced British detectives. Child protection campaigners allege Portugal's cultural complacency about paedophile crimes allows kidnappings to continue.

British couple, or sold to adoption

The second most likely theory, according to British officers, has gained currency in the past three days amid reports of a couple "of British appearance" fleeing after being spotted trying to photograph young blonde girls in Sagres. Local reports also suggest that police sniffer dogs followed a scent from the McCanns' apartment to a British couple's apartment at Ocean Village.

Family involvement

Dismissed as a possibility by Portuguese police. Ch Insp Sousa clarified on Thursday that the McCanns are not suspects. He said the couple had been asked to attend the police station simply to review their statements.

Mentally ill abductor

There have been several sightings of a lone woman outside the McCanns' apartment on the night of her disappearance. Former detective David Hill, however, thinks this theory improbable. "If there was a mentally ill woman out there, somebody would have told police," he said.

Madeleine wandered off

Portuguese police would not initially confirm that Madeleine had been abducted, giving rise to the theory that she walked off. It is understood that the door to her apartment was open. But she would have walked within view of her parents, and British detectives consider the theory unlikely.

Nine days of anguish

* THURSDAY 3 MAY

Madeleine McCann vanishes from hotel room where she has been left by her parents. Kate and Gerry McCann call police to report the disappearance.

* FRIDAY 4 MAY

Police launch search, using sniffer dogs, and alert airports.

* SATURDAY 5 MAY

Three British officers arrive in the Algarve. McCann relative accuses local police of being "uncommunicative". Police say they have a sketch of a suspect.

* SUNDAY 6 MARCH

Questions are raised about the veracity of the suspect's image.

* MONDAY 7 MAY

Reports emerge that a balding, "English-looking" man was seen dragging a girl towards a nearby marina. Mrs McCann makes emotional plea.

* TUESDAY 8 MAY

Portuguese media claim police are investigating British paedophiles. British ambassador meets the McCanns and defends the investigation.

* WEDNESDAY 9 MAY

Crimestoppers says it has had hundreds of calls, including four leads. Inquiries focus on whether girl was snatched by two men and a woman.

* THURSDAY 10 MAY

Police start to wind down search around the resort to concentrate on other leads.

* FRIDAY 11 MAY

Parents say they will leave "no stone unturned".