At a time when Russian paintings were usually religious or highly moralistic, this picture was secretly scandalous. The leg at the rear of the picture could not possibly belong to the gentleman in the picture so there must be a third person on the bed behind them, and from its skin tone the hand on the lady's hip must belong to that third person. The lovers are clearly unaware of this third person, unlike the servant who is peering around the door. There are other clues too - which may be recognised by art students but which I cannot remember - which overall tell the story that the servant has set it up for his master to hide in the bed waiting to catch his wife being unfaithful with her lover.