Moritz and Dad want to become superheroes. To do that, they need to train, says Dad, because as a superhero, you need courage, determination, and brains. That's why the two of them decide not to go away for summer vacation, but to focus entirely on their training: conquering magical objects. They set each other challenges, tests of courage that require all their skills. They defeat the wild Lotti from the neighborhood, tame a hellhound, and outsmart their mean landlord. In the end, a treasure chest full of items bears witness to their trials of courage, and Moritz and Dad are finally superheroes. Well, almost.