Margarita's husband sold the company, bought twelve rare colored diamonds with this money and died suddenly. After the funeral, the widow decided to look at the stones, but they were not in the safe. But they found a code left by the deceased, which the widow could not decipher. Margarita had no choice but to turn to amateur detective Katarina Kopeikina. The problem is that right now Katarina is investigating a serious crime - a murder disguised as an accident. And still, the detective will have to pay attention to solving the diamond mystery. At least for the purpose of looking at real treasures...