The day after the funeral of the famous philatelist, two men in police uniforms come to his widow and take away a box with valuable stamps. They are particularly interested in Orange Mauritius. While the conversation continues in the hallway, the philatelist's grandson, sixth-grader Lenya, manages to replace the original stamp with an inept photocopy. In this form, the album with stamps gets to the false policemen...

The corpses of two young people who came to work from Lugansk are found in the apartment. Jeannette discovers a potent poison in a vodka bottle on the table, and Artyom finds an ancient gold coin on the floor. A well-known archaeologist sheds light on the case. He tells Lena Brusnikina about the treasure of the merchant Voskoboinikov, hidden in the Moscow region at the beginning of the twentieth century. Obviously, the guys stumbled upon this treasure, which other people were interested in...