Lena and Willi visit the somewhat strange Madame Brickabrack during their vacation. The town-famous, elderly lady owns a thrift shop filled with all sorts of curiosities. Among them is an old wardrobe that supposedly allows you to travel back in time. And indeed: just moments ago, the children were in the magical wardrobe, and now they suddenly find themselves in the middle of a country road. There, they are already awaited by siblings Martha and Karl, who mistake them for relatives. However, Lena and Willi have little time to adjust to the everyday life of the 1920s: an arsonist is causing havoc in the area, instilling fear and panic among all the villagers. The suspicion falls on the peculiar blacksmith. Lena, Martha, Willi, and Karl form the "Four-Wing Gang" and soon realize that the case is not as simple as it seems. Will they manage to catch the real firebug?.