It was decided to combine a series of burglaries into one case, as they are connected by two nuances. Firstly, robbers enter apartments not with the help of lock picks, but with the help of a key, and secondly, all robbed businessmen's wives visit the same aquacenter "Aquamarine". Lena, under the guise of a bored lady, and Artyom, with a desire to swim, go there. However, Mukhtar makes some adjustments to his plans: he hides the bathing trunks of his beloved master…
 

Olga's birthday, her loving husband Boris wants to celebrate on a grand scale in a restaurant on the ship and invites many guests. Boris solemnly presents his wife with a very expensive diamond pendant, but the decoration soon disappears under mysterious circumstances. Artyom, Lena, Vadik and, of course, Mukhtar begin an investigation, but Mukhtar suddenly loses track…