Polina Serova unexpectedly became a secret agent of the Russian emperor! In the company of officer Alexei Kaverin, she arrived in Paris, intending to complete her first task - to obtain secret documents that were extremely important for Russia. She and Alexey came to a masquerade ball in a mansion where a box with documents was hidden, but instead they found another one, with some old letters... In order not to keep evidence, Alexey got rid of the unnecessary box, but it soon became clear that these letters indicated the way to the treasures of the French crown, which King Louis Philippe himself is looking for! Now Polina and Alexey will have to look for what they so recklessly threw away. And none other than the most famous detective of all time will help them - Vidocq!