Baroness Amalia Korf, the secret agent of the Russian emperor, has just returned from Paris after a successfully completed mission—she managed to intercept compromising photographs of one of the ministers who was having an improper affair with the Italian singer Lina Cassini. But that turned out to be not enough, because Lina is going to Petersburg for tours! How to prevent the high-ranking official from meeting his mistress again? Amalia proposed a simple solution—to divert the singer’s attention to another gentleman. For the role, they chose… her uncle Kazimir, a well-known ladies’ man and heartbreaker! The baroness managed to obtain invitations to a celebration at the German ambassador’s residence, 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…