Uninvited Guests.

Viktor and Olga have long been living in a hateful marriage. They've finally paid off their mortgage and seem to enjoy life in their own apartment, but the neighbors on the side turn out to be too passionate for a new building with thin walls. One day, those same neighbors come to the couple with an offer to have sex together. Viktor and Olga refuse, then agree, refuse again - and the incident seems to be over, but a third couple has already arrived, constant "close friends" of the neighbors on the side.