Apfelland is a small but beautiful country surrounded by Russia, Austria, and Germany. Vel is a boy who lives in the capital, Charlottenburg. He happens to help a girl Frid. She was kidnapped because radium mine was found in her grandfather's abandoned mine. Aiming at the radium mine, various people gather there, for example, an American who wants to make money, a Polish woman disguised like a man who wants to earn money for the revolution, and the ministry of Apfelland who plots to affiliate with Germany. Vel and Frida are involved in their plots, and they know the secret of the mine.