Billy and Sir Hubert turn out in the course ""cat after assistance hour"" to the gauner Len and Denz, which found straight in the cellar of a house a treasure. In this house the Katzenomi with its favourites lives. Mr. Big, the Boss of Len and Denz, is the owner of the building and tried now to drive her and the other tenants out in order to be able to lift in all peace the treasure. Billy and Sir Hubert take care of the thing and are - after some existed adventures - able to prevent the evacuation and to deliver the gangsters of the police.