In The City Of Ember, Lina has discovered an important document. However, her little sister, Poppy, has chewed up quite a bit of the document and left holes in it, leaving Lina struggling to decipher the words on the paper. When she realizes that the word 'Pipeworks' looks like one of the words on the document, she decides to pay Doon a visit. After all, that's where he works.
Lina invites Doon to her home to take a look at the document. Hopefully, he can help her figure out what's on the paper. Lina tells him that she has named the document, 'The Instructions.' When Doon first sees the document, he doesn't say anything. Even though Lina continues telling him about her suspicions that the document contains instructions on how to go somewhere, Doon still remains silent. It turns out that Doon is mesmerized by the contents on the document, and he is trying to figure out the exact words on the paper. He talks to himself while he is trying to make sense of the document. Eventually, he tells Lina that he believes the document is an important one.
Lina feels especially inspired that the word 'door' on the paper refers to the door out of Ember. Doon questions why such a door would exist in the Pipeworks; however, he suddenly remembers that he did see a door where there shouldn't have been one: in Tunnel 351. Both Lina and Doon agree to investigate this mysterious door the next day in the Pipeworks.