During a trip on the port area Billy loses the patience with its friend Sir Hubert, which continuously only remembers to full-slam itself shut with raw meat. From a fish crate at the head met, Billy tumbles on board the ship ""the merry Mauser"". There the captain a Betaeubungsmittel gives to it. It wants to use Billy as ship cat against rat troubles. Billy is pushed into the ship belly and the ship down puts. After a first collision with the rat king Billy discovers that in the belly of the ship kidnapped Rassekaetzchen sits in cages, which are to be sold abroad. Meanwhile Sir Hubert jumbo jet alarmed, which discovers its friend soon on the ship. When the coast guard comes with a routine control on board, Billy sets the ship on rock, schmeisst the rats over board, saves the kaetzchen and is the hero of the daily.