Baroness Amalia Korf, a secret agent of the Russian Emperor, has just returned from Paris from a successfully completed mission - she managed to intercept incriminating photographs of one of the ministers who began an inappropriate relationship with the Italian singer Lina Cassini. But this turned out to be not enough, because Lina is going to St. Petersburg on tour! How to prevent new meetings between a high-ranking official and his mistress? Amalia proposed a simple solution - to divert the singer’s attention to another gentleman, whose role was chosen... her uncle Casimir, a famous womanizer and heartthrob! The Baroness managed to get invitations to a celebration in the house of the German Ambassador, where Lina was supposed to sing. But the evening ended unexpectedly for everyone... with the murder of Michael Ritter, Amalia's German colleague! And of course, she was the first to come under suspicion...