A girl gave a boy a fan. Oh, that sounds like the beginning of an old-fashioned romance! But in fact, it is the beginning of a detective story. Because Dasha Lavretskaya and Petka—the very boy who was given the fan for repair—conduct real investigations. This case turned out to be one of the most complicated: on the scorched plate of an old fan there was a French inscription: “The key to the secret.” Dasha and Petka had no doubt that the secret itself was hidden in the tattered trunk the girl had inherited. But it disappeared…