Everyday, Pashupati Kunwar sits at a post on the India-Nepal border scanning every girl who crosses over. She keeps her eyes peeled for any who may have fallen into the hands of traffickers.
"I can identify the vulnerable lot in a crowd of thousands, sometimes from their behaviour, sometimes from their footwear," Kunwar, who has been in this job for six years, says. A new dress, or pair of shoes, on a girl from an apparently poor family is a giveaway.
The Nepal police have just caught an old man who was trying to take a girl to India, saying she was to go to Dubai to work.
This is a common occurrence at the two check posts on the Indo-Nepal border in the eastern Uttar Pradesh districts of Maharajganj and Bahraich.
Hundreds, perhaps thousands, cross over undetected every year into India, which is the centre of a flourishing international illegal trafficking market.
With the border unfenced and largely unmanned, preventing trafficking of women is nearly impossible.
Sewa, a voluntary group, mapped 1,268 unmanned routes on the Indo-Nepal border that aided traffickers. Jata Shanker, the founder president of Sewa, says: "We have to ensure safe migration to check trafficking. We have now come up with the toll number 1800-180-1000 on which girls in distress can contact us."
Though women like Kunwar, from the Nepali anti-trafficking group Maiti, receive help from the police on both sides, trafficking agents constantly devise ways to cross over.
"Girls are categorised according to age and looks, then sent to hotels, homes, brothels or third world countries to work as bar girls, house maids or prostitutes," said Bhawani Rana, the president of the voluntary group Sathi, headquartered in Kathmandu.
According to estimates by humanitarian agencies, there are up to 200,000 Nepali women in Indian brothels. Some 7,000 are sold in India each year.
According to a UN study, the average age of girls in the flesh trade from Nepal has come down from 14-16 years in the 1980s to 10-14 years in the 1990s. Nepali journalists did a year-long campaign in 2003 to create awareness.
"The girls entertain five to 10 customers a day and get Rs 150 to Rs 500 from each. Their age and looks decide the amount. While the women running the racket pocket the entire money, the girls survive on tips," says Prabha Khanala of Maiti.
She declined to allow access to any of the rescued women, saying: "They are in a shocked state. It takes time to win their confidence as they have been betrayed by all - family and friends, Indian or Nepali."
Not all girls choose to go back home, where they often face abuse. In 2007, Maiti activists intercepted more than 2,000 girls, of which only 42 could be persuaded to return home. "We are pressuring the government to tighten laws on violence against women…. Many parents refuse to accept them and their torture continues. So we are now engaged in their rehabilitation," says Rana.