14 year old Anna-Lena accompanies her father Friedrich to the burial of her grandmother, which takes place in a small town in Germany's Ruhr Area. The girl is in a bad temper, because her father wants to spend the time in the house of his puppy love Ulrike and her son Lutz. Lutz seems to be quite uncool, but during the story he turns out to be a hero, when Anna-Lena and Lutz get into a mysterious adventure, which leads them back to the 40s and starts in the abandoned house of her grandmother. They discover a secret room, where obviously somebody has been hidden during World War II. But who was this person? And what does Lutz' grandfather Rudolph know? Anna-Lena and Lutz find out, that their family histories are intimately connected with each other and incidentally they learn their first lessons about love, jealousy and true friendship.