Berlin - A man looks with interest at the child sitting in front of him in the metro, as a voice asks off-screen: "Do you like children in ways that you shouldn't?"
"Help is available," adds the advertisement broadcast on German television and over the internet, urging people who feel sexually attracted to children to join a unique therapy programme called "Don't offend" (Kein Taeter werden).
Launched some 11 years ago, the largely publicly funded project by Berlin's top university hospital Charite calls on paedophiles to undertake a treatment that helps them control their urges.
More than 7,000 people have sought information on the programme which is offered in 11 centres across Germany.
Of these, 659 people have undertaken the therapy, with 251 completing the entire programme. Another 265 are currently being given treatment either in group or individual sessions.
The German initiative is unique because it deals with potential sex criminals, or those who have already committed abuses but have managed to escape justice.
Other programmes deal with convicted paedophiles who have also been issued specific orders to seek medical care.
Klaus Beier, who leads the prevention network as well as Charite's sexual medicine institute, has no illusions about the programme.
"Paedophilia is not curable," he said.
"But it can be treated," he added, stressing that "a paedophile can learn to control his urges."- Treating urge to prevent crime -
The project is grounded on the principle that sexual attraction to children is a medical problem, and as Beier said, "not a crime" until the urge is acted upon.
The World Health Organization too classifies paedophilia as a "sexual preference disorder".
Over one or two years, during two-hour sessions every week, the patient is taught to develop strategies to stop himself from acting on his tendencies or from consuming child pornography.
The programme also helps the patient to acquire a level of empathy towards potential victims, which could go towards dissuading him from hurting them.
The patient can choose to remain anonymous throughout the treatment, even with his therapist, and at the end of the programme, he can request follow-ups.
Medical help, such as chemical castration, is also offered on a voluntary basis.
Scientists from around the world including countries in North America as well as Switzerland and India, have been watching the project with interest.
"In France, we are still at the starting point on creating a programme that is similar to Germany's," said a psychiatrist at France's health and medical research institute Inserm, Serge Stoleru.
He said the response from authorities had been that "paedophilia is a tricky subject."
But even in Germany, one of the countries scarred by a massive paedophile priest scandal in the Roman Catholic Church, the therapy programme is controversial.
Not only is there strong societal pressure against the programme, Beier said that even in the pharmaceutical world, there is "great reticence" towards developing medicine for paedophiles that could take effect rapidly.
However, Jerome Braun, who leads a child protection foundation called Hansel and Gretel that co-funds the therapy programme, said that prevention work must not only be targeted at bringing awareness to potential victims in kindergartens or schools.
"It should also look at potential criminals because each act prevented is a child saved," he said.