At the beginning, Milo gets home, bored again, and notices a box and letter on his be labeled Milo and he sees a tollbooth. So he decides to go in because he has nothing else to do.
After entering a new magical world, Milo meets a dog named Tock and learns the tale of Princess Rhyme and Reason. Once he comes to a kingdom named Dictionopolis he and Tock enter.
There Milo and ock meet King Azaz, the king of words and propose that they go find the Princesses so that Azaz and his brother, The mathemagician will finally get along. The King agreese and the two go to the word market only to find new friend, the Humbug, to go on the journey.
Just before they leve Azaz gives Milo a box of letters to help him. Once Milo, Tock and Humbug make it to Digitopolis they convinces the Mathmagician to let them rescue Rhyme and Reason and the Mathmagician give Milo a magic pencil to help along the journey.
On their way, Milo, Tock, and Humbug get trapped by the Demons and have a hard time escaping. Luckily they are able to make it to the Castle in the Sky.
The three are able to save the Princesses but Milo has to return home and promises he will be back someday.