The major problem in The Tale of Despereaux is the unfriendly relationship between the mice, the rats and the humans. Roscuro the rat caused the death of the Queen which forced the King to outlaw all rats. During Roscuro’s escape after the death of the Queen, Princess Pea spoke harshly towards the rat and because of this the rat grew to resent the Princess. After these events, Despereaux, the unusual mouse with unusual physical features was born. Despereaux encounters the princess and gets attracted to her. The mouse is sentenced to the dungeons to be eaten by rats because of the relationship with the princess. Later in the story, Despereaux overhears a conversation between Roscuro and Mig, the royal maid charged with delivering food to the dungeon guard, with the intentions of harming the princess. Due to Roscuro’s trickery both Mig and the princess are held captive in the dungeon and Despereaux goes to save them. Despereaux gets an opportunity to kill Roscuro using a needle handed to him by the threadmaster who encouraged him when he was sentenced to the dungeon. The princess asks Despereaux not to kill Roscuro and the story ends with the main characters seated at the banquet hall having soup, in what seems to be a reunion of the mice, rats and humans.
The efforts of Despereaux help in solving the problem between the mice, the rats and the humans.