Curiouser and curiouser: The teenager imprisoned for more than eight years

So what really happened to Natascha? She will appear for the first time on TV this week, while bidding for a first newspaper interview has hit £300,000. By Martin Hodgson and Ruth Elkins

The Austrian teenager imprisoned for more than eight years in an underground cell will tell her extraordinary story in public for the first time this week.

In an exclusive 20-minute interview with the state-owned ORF TV channel, Natascha Kampusch is expected to reveal further details of the eight-year ordeal at the hands of the obsessive loner who made her his slave - and to address some of the details of her story which, 11 days after her escape, remains vague and contradictory.

Disturbing questions are being raised about her family life before the abduction, about the ordeal itself - and about the degree of control exerted over her by the team of social workers, psychiatrists and government officials treating the teenager.

Natascha, since her escape, has had just one brief meeting with her parents, Ludwig Koch and Brigitta Sirny, but reports suggest that it was not the joyous reunion that might have been expected, and a second meeting was cancelled at the last moment.

One possible explanation may lie in Natascha's unhappy family life before the kidnapping, said Walter Poechhacker, a private detective who wrote a book about the case.

"Something must have happened in that family. Something that had to be hidden," he said. "When the child begins to speak there will be surprises."

Over the past week, a picture has started to form of Natascha's deeply unhappy childhood at the time of the abduction. Both parents attest to an unfaltering devotion to their daughter, although her father is charging reporters €1,500 per interview. It has also emerged that following her disappearance in 1998, investigators briefly looked at allegations that she may have suffered sexual abuse at the hands of her own family.

There is no suggestion that the rumours were true, but the revelation has fuelled speculation surrounding Natascha's apparent reluctance to be reconciled with her family.

Before her disappearance, Natascha's last conversation with her mother ended in a row and a stinging slap across the face. At the time, Natascha was a chubby 10-year-old who was bullied at school for being overweight. Following her parent's acrimonious separation, she had gained more than a stone and a half in just over a year.

After the separation, Natascha lived with Ms Sirny on a grimy housing estate 20 minutes and a world away from the classical elegance of Vienna's city centre.

There, amid the patchy lawns and looming towerblocks, she caught the attention of the 36-year- old handyman Wolfgang Priklopil. This week, neighbours described him as a fastidiously dressed loner whose closest relationship was with his domineering mother, Waltraud.

On the morning of 2 March 1998, Prikopil intercepted Natascha as she walked to school, bundled her into a white Mercedes van and drove her to his suburban house in Strasshof, north of Vienna - and the underground cell that was to become her home for eight years. Police photographs showed the tiny chamber was fitted with a bed, a toilet and a sink.

From the moment of the abduction, Priklopil used lies and threats to manipulate his young captive, telling her that her parents had refused to pay a ransom, and that the house was booby-trapped with bombs to prevent any escape attempts.

Psychologists have drawn a profile of Priklopil as a man obsessed with control, who used a system of rewards and punishments to dominate Natascha. But the true nature of their relationship may have been more complicated than a simple scenario of master and slave.

Natascha has refused to answer "intimate questions" about her relationship with the man she came to call "Wolfi". Forensic tests have confirmed that Natascha did enter Priklopil's bed, but the investigators have not yet found any conclusive evidence that their relationship was sexual.

Uncanny parallels have emerged between the case and the plot of a novel by the British author John Fowles. The Collector tells the story of an impotent butterfly collector who builds a cell in his basement, kidnaps an unhappy girl, and attempts to make her love him.

Incarcerated in the cramped 6ft-by-10ft cell, and uncertain that she would ever be free, Natascha underwent eight years of emotional "torture" , according to the psychiatrists who are treating her. Reports in the Austrian press say that Natascha's worst moments came when Prikopil left the house, because she was never sure if or when he would return.

Later on in the eight-year captivity, Priklopil gave Natascha a degree of freedom, allowing her upstairs to watch Mr Bean videos with him, and even letting her out of the house to shop alone for groceries.

Last week, several witnesses came forward to say that they saw the young woman in Priklopil's house or garden, but did not recognise her, despite the massive police hunt for the missing girl.

After Natascha escaped on 23 August, Prikopil spent his last hours in a blind panic, driving drunk around Vienna with Ernst Holzapfel, his partner in a construction company. Holzapfel told reporters that he had expected Priklopil to turn himself in to police.

Instead, the kidnapper committed suicide by throwing himself under a train, taking with him any hope of an explanation for Natascha's horrific ordeal.

According to Professor Max Friedrich, who heads the team caring for Natascha, she is still "deeply traumatised" by her experience and and is still suffering flashbacks.

Natascha's father has filed a claim for a share of Prikopil's estate as compensation for her suffering.

Social workers treating Natascha say that she may not decide to meet her parents again for weeks or even months.

Detectives were allowed to question the 18-year-old in three 20-minute sessions this week, but they admitted that many "burning questions" about the case remain unanswered. Meanwhile, bidding for her first newspaper interview is now said to have reached half a million euros (£330,000).

Natascha has spent the days since her escape coccooned in a sanatorium outside Vienna. Psychologists say she has been trawling the internet in an attempt to catch up with some of what she has missed.

This weekend, she was set to meet a carefully selected group of Viennese teenagers, in her first contact with people of her own age for eight years.