A Good Boy (2008)

After his mother's death, 17-year-old Sven moves in with his dad Achim, a taxi driver who had divorced his mother several years earlier. It is not easy for Achim to get used to an adolescent around the house, especially since Sven hardly speaks to him. But Sven does well in school, and Achim hopes that time will bring them closer together. It is Achim's girlfriend Julia who first senses that something is wrong with Sven. Why, she wonders, does he always hang around with younger boys? Why does he not have any friends his own age? She suspects that he is gay. The truth, however, is more nuanced--and chilling: Sven has pedophile tendencies. Proof is soon found on videos that shocks and sickens Achim. Sven himself is shattered and regrets his actions. Julia suggests therapy, but Achim is convinced that he and Sven can handle this together. But he is wrong. Though Sven practically begs his father to lock him up in his room, Achim has confidence in his son--a confidence that soon turns out to be ill placed.