Loitering by the side of the dusty motorway in a skimpy lilac dress which hung loose from her birdlike body, the girl looked lost and painfully alone in the dark Brazilian night.
It was 1.30am and there was no obvious explanation why she should be on a nightmarish stretch of road rather than asleep in her own bed.
But the deeply disturbing truth was this. At the age of 11, Leliah, with her childlike and fragile limbs, was selling herself for sex to any truck driver prepared to pay.
When he’s finished he throws me out of the cab’, she said, showing her battered and bruised elbows. ‘Sometimes they let me climb down, or sometimes they just kick me out onto the concrete.
‘But I never sell myself short. I charge 25 reals (£10) a time’.
For British journalist Matt Roper, this chance meeting with Leliah was to change his life. He drove off along the BR-116 motorway, a merciless 2,700-mile stretch of road spearing up the coast of Brazil from Rio de Janerio to Fortaleza, in a state of profound shock.
Later he decided to investigate and write about the forgotten children who eke out a living on the Highway to Hell.
And despite being a hardened news reporter, nothing had prepared him for the scale of depravity he was to uncover.
Leliah was just one of thousands of girls – some as young as nine - sold for sex every ten miles along the BR-116. Many are prostituted by their own families. The cheapest fee for a transaction is £8.
Working with his friend Canadian country singer Dean Brody who had been with him on the night he met Leliah, Roper set up a charity called to Meninadança provide refuge for the children who had been forced into prostitution.
They established The Pink House in Medina, where visitors can talk about their experiences, take dance and beauty classes and find support.
Run by Ms Marques, nearly 100 girls aged 11 to 17 have been through its doors since it opened at the beginning of the year, with around 60 coming to the project every day.
Meanwhile, Roper had had a second encounter with the young girl who was prostituting herself so her mother could afford cigarettes.
Now she was 15, seven months pregnant and dancing for a scruffy, unshaven man in a brothel.
‘My mum never cared about me. She was just interested in using me to buy her cahaca. So I ran away. At least now I can keep the money for myself’, she told him.
With the help of Ms Marques, Roper persuaded Mariana that she did not have to stay in this sordid place. After persuading the town’s judge to forcibly take her away from the mother who was exploiting her, the journalist and his wife took her in and, despite being unable to keep her baby, she has now settled into their home.
Her 16th birthday was celebrated with a huge party.
‘I wept as I saw her, beaming radiant, surrounded by new friends and family. I could hardly believe she was the same girl we had found less than a year ago, dancing lifelessly inside that dark oppressive roadside brothel,’ Roper said.
Later, Roper and his wife took another girl into their home who workers at the Pink House had discovered was in danger. Nathane, 13, was sleeping in friends’ houses after her mother died, and was on the brink of falling into the dark work of child prostitution that had snared so many.
Despite successes with Mariana and the Pink House, there was one girl that Roper could not forget.
Haunted by Leilah, the ghostly girl in the lilac dress, the journalist set out to find her.
It was too late. Still a prostitute on the Highway To Hell, she was now heavily addicted to crack cocaine and desperate for cash to buy drugs.
When Roper refused, she became furious and snarled: ‘Don’t bother coming back.’