Pere Ubu, along with Mere Ubu and Captain Bordure, plot the killing of the King of Poland. Pere Ubu poisons Bordure's men, who have assembled at a sumptuous feast, by providing an excrement covered toilet brush for all to taste. The act ends with Pere Ubu demanding that Mere Ubu, Captain Bordure, and the other conspirators "swear to kill the king properly."
Pere Ubu attacks and kills King Venceslas of Poland. Queen Rosemonde and her youngest son, Bougrelas, escape to a mountain cave, but the Queen dies. The dead ancestors appear to Bougrelas and demand vengeance, giving him a large sword.
After some prompting from Mere Ubu about sharing some of his newly ill gotten wealth, Pere Ubu throws gold coins to the crowd. Several are trampled in the mad.....
