Berlin, here we come! Finn and Joanna are participating in the first children's parliament at the Berlin Bundestag. Here, they get to help decide whether a large adventure playground or a game house will be built next to the Reichstag. But the siblings quickly realize that something is not right during the sessions. Many young parliamentarians from the game house faction suddenly have the latest smartphones and tablets. Others are absent from the meetings. Are the children being bribed? It becomes clear, especially when Finn and Joanna are threatened by shady characters, that this is about more than just a game house.