The Lost Son (1999)

Xavier Lombard is a world-weary private eye in London, in exile from his native Paris; his best friend is Nathalie, a high-class call girl. He gets a call from an old friend from the Paris police department, now a businessman whose brother-in-law is missing. The missing man's parents hire Xavier over their daughter's objections, and quickly he finds himself in the realm of children's sexual slavery. He guesses that the lost son is dead and shifts his focus to finding and breaking this lucrative business of child trafficking. He involves a reluctant Nathalie to hunt "the Austrian," the shadowy head of the business. Violence erupts quickly, and Xavier soon has little more to lose.