Harpia with a propeller

Dashа Vasilyeva, a private investigator enthusiast, was visited by her friend Lena Gladysheva, who accused her of secretly slipping twenty thousand dollars into her mailbox. But it wasn't Dashа! Lena's husband Oleg disappeared a year ago under mysterious circumstances, and now someone had planted the money supposedly from Oleg. The friends decided to find out from the concierge who had left the envelope. She said it was the postwoman Sonya. While Dashа was talking to Sonya, some thugs killed the concierge and seriously wounded Lena. The postwoman described the man who handed her the money. It seemed to be... Oleg!