Rico, Oskar und die Tieferschatten (2014)

Preteen simpleton (Fede)Rico lives in a Berlin apartment with his mother, a single escort 'employee', obsessively clinging to post-its and procedures to compensate for his utter inability to think properly, leading to very unequal relationships with various neighbors. When he bumps into bright, younger but paranoid (autistic?) Oskar, the boys strike an instant friendship. Rico begs to stay home alone while his mother travels so he can ask Oskar over, but when Oskar doesn't come, Rico thinks he's become the latest victim of the city's serial child-abductor. Far-fetched 'clues' lead him to suspect anyone, even super-nice new neighbor Simon Westbuhl, and investigate clumsily all over the neighborhood. By coincidence, he actually finds Oskar in need of rescue.