More than one million children are exploited every year by the international sex trade, according to UN estimates.
In Central America the problem has been growing, with sex tourists attracted to the region by ever-cheaper flights as well as easily circumvented child protection laws.
One man, a British charity director, has dedicated himself to tracking down the offenders that governments have failed to prosecute.
Bruce Harris, of the Catholic children's charity Casa Alianza, wants to stop the area from becoming one of the world's biggest centres for child sex tourism.
Mr Harris is based in Costa Rica where, he says: "We get plane loads of sex tourists coming in".
"They leave millions of dollars in the country. Sex tourism is big money."
Paedophiles have been able to exploit loopholes in Costa Rica's child protection laws and, for years, the chances of being caught and punished were almost non-existent.
In a country where the authorities seemed reluctant to pursue offenders, child sex tourists appeared likely to get what they were looking for: anonymity and immunity.
After years of persuasion, Mr Harris finally managed to convince the government that the problem needed to be acted on.
Sting operations
He has recently filmed pimps undercover, set up elaborate stings to trap internet paedophile rings and harangued governments to change laws and act against offenders.
But some successful convictions - helped also by tougher laws and the appointment of a special prosecutor - have led to death threats for Mr Harris.
The country is now marketing itself as a modern holiday destination and trying to show that times are changing, but two of Mr Harris's biggest cases will test the country's resolve.
Madame Siani Monge Munoz - accused of being Costa Rica's biggest child pimp - has finally been arrested, 10 years after first being investigated by Mr Harris.
It is said she has a secret list of clients that includes major public fig
