This is an automatically translated description

From the publisher:

The heroes of the story - a fragile young violinist Olenka and her friends - Anton, Sasha and Serhiy - while on holiday in a camp on the Black Sea coast accidentally learn about the secret of the jewels of the famous Milady, the heroine of the novel about the Three Musketeers, hidden nearby. At night, the friends secretly set off in search of the treasure, but find themselves in a whirlwind of exciting adventures. They will have to make a dangerous journey to the smugglers' cave and engage in a real fight with the thieves of museum valuables.

Who will win in the eternal battle of good and evil - cunning and hatred, or sincerity and friendship....