The Konstantinovsky Palace in Strelna keeps many secrets. But the main one is the jewelry box of Josephine, the Grand Duke’s favorite, hidden in a secret place... Tanya often heard this legend from her grandfather, but she doubted that the treasures really existed. But Roman Dvoryankin, with whom the girl had been unrequitedly in love for many years, believed the old historian and, during the reconstruction of the palace, got a job as a simple installer... Driven to despair by Roman’s indifference, Tanya decided to break up with him and finally become free. And soon the girl was arrested - on the night of their last meeting, Dvoryankin was stabbed with a knife, and a mysterious box was stolen from his safe.