At the Ronov castle, the archive-keeper professor Nykl (Milos Nedbal) is searching for the lost painting The Naked Shepherdess by the famous Fragonard. Nykl is just about to disassemble the mantelpiece in the knight's hall, convinced that the painting must be hidden somewhere inside. His efforts, however, meet the strong disapproval of the castle manager, Anna Juzová (Jirina Petrovická), who knows very well where The Naked Shepherdess is. She wants to get hold of the painting herself, to emigrate and smuggle it along. In fact, Anna deals with forgeries of the most distinguished old masters, selling them abroad. The copies are made for her by the painter and restorer Maudr (Martin Ruzek) and the certificates of authenticity are issued by Anna's companion - expert Laburda (Karel Höger). One day, Anna is found murdered in front of the castle's fireplace.