Roddy St. James lives a carefree life, he is a house mouse who does not have to do anything, but only enjoy his ideal conditions. The main character lives in a rich house, and of course he has everything he needs for a decent life. In such conditions, the mouse feels like an aristocrat, and behaves accordingly to his opinion. Only now he is overcome by constant loneliness, the owners often forget about him, and sitting in a cage alone is not very comfortable.

One day Sid sneaks into the house, this mouse has lived in the sewer all his life and did not know what etiquette was. After seeing how Roddy lives, a guest who arrived from nowhere, declares that he remains to live here and is not going anywhere from here. The tenant of the house does not want to leave the dirty girl at home and decides to flush the uninvited scoundrel into the toilet, but at the moment of the fight, he himself falls into the sewer. From this moment on, amazing adventures begin for the main character in a world unknown to him.