Возвращение Мухтара S11E23 - Пейзаж в тумане

Valentin Baranov receives a message that a painting by Aivazovsky has been stolen from his safe. The kidnapper offers to return it for 5 million rubles and informs that there is now a copy of the painting in the safe. The detectives, having studied the case materials, come to the conclusion that there was no abduction. And there was a conspiracy in which one of the people closest to Baranov participated. But who exactly?