When Natascha Kampusch made her bid for freedom on 23 August 2006 after eight years held captive in a seemingly ordinary Austrian suburban house, her story horrified and astonished the entire world.
How did she survive a childhood locked in a cellar? What sort of young woman had emerged? What kind of man was Wolfgang Priklopil, her abductor - and what demands had he made of her?
As the days and weeks passed and Natascha's TV interview failed to quell the curiosity, so the questions began to change.
What exactly was the relationship between abductor and hostage?
Why had Natascha waited so long to escape when it seemed there had been other, earlier opportunities?
Did Natascha's parents know Priklopil before he kidnapped their daughter?
Allan Hall and Michael Leidig have tracked the story from the days of the 10-year-old's disappearance.
They have spoken to police investigators, lawyers, psychiatrists, and to the family members closest to Natascha.
They have come as close as possible to uncovering the full, shocking story.
It is a story that tests the limits of our understanding of how human beings behave - and makes our hearts bleed for the plight of an innocent child caught up in a horror story almost beyond our imagining.