In 1826, a certain Countess de Gache, a former lady-in-waiting at the French imperial court, died in her Crimean home. Her death caused a stir in high society, as the 70-year-old woman owned an expensive necklace intended for Marie Antoinette, the wife of the French king. The situation was exacerbated by the fact that the Countess de Gache had unlawfully acquired the ornament and was not actually a countess.

Jeanne de Lamotte, who grew up in a poor family, quickly entered high society thanks to her energy, intelligence, and beauty, and at just over 20 became a lady-in-waiting at Marie Antoinette's court. There, she made useful connections and, using cunning and charm, began to engage in financial schemes. However, as the saying goes, her greed led to her downfall. De Lamotte set her sights on the queen's diamond necklace.

One day, she approached jewelers, claiming that the empress wanted to purchase an expensive ornament. After receiving the necklace, she stated that she could not pay immediately and that Cardinal Louis de Rohan would handle the payment, misleading him by saying that Antoinette was asking for his help. The cardinal partially paid in cash, and for the remaining amount, he issued promissory notes. When the time came to settle the debt, the deception was uncovered. De Lamotte was caught, tortured, and sentenced to death, but she managed to escape abroad during the revolution.

In Russia, she settled under the name Countess de Gache. Alexander I regarded her with disdain, and by his order, the fraudster was exiled from Petersburg to Crimea. There, she lived comfortably, but the origin of her wealth remained a mystery, and the necklace was never found in France. De Lamotte was buried in a local cemetery, but during the Soviet era, a highway was built over it. Nevertheless, for a long time, people tried to find the diamond pendants that, according to rumors, the countess buried before her death.