The Underground Man is convinced that he is doing the right thing by his workers. He asks the King for permission to fill in the hole in the wall. He gathers the best blacksmiths in the city and uses them to build a giant furnace to seal the hole. He also uses arsenic to make the furnace more durable. The underground man knows that the monster will never escape. He knows that those who have been chosen from the beginning to serve the monster are willing to die for his sake. He realizes that they are no longer afraid of the monster, and that he will be able to trap him.