Doon wanders the Pipeworks by himself a lot, now that he's gotten the hang of getting his work done quickly.
He finds interesting bugs, like his dad had suggested he might…but then he accidentally squishes one of his new finds when the other workers make fun of him for collecting bugs, causing him to angrily leap up and shout back. Gotta love those unintended consequences.
While exploring, Doon finds a roped-off tunnel, but goes in anyway. There's nothing but a locked door, and a hatch in the ceiling he can't reach. He finds some mysterious grooves on the riverbank, too, almost like writing.
Frustrated at his slow process in the Pipeworks, Doon decides to try working on a kind of moveable light. He goes to the Ember Library to look for information on fire.
People in Ember didn't have much experience with fire; occasionally a cloth left near an electric stove might erupt in flames, but that was about it. Very few people knew how to make a fire on purpose, or what to do to keep it burning.
Doon doesn't find much on fire, but he does find an interesting book of old phrases. Words like "hogwash" are a complete mystery since no one in Ember knows what a hog is or why you'd want to wash it, for example. Being "all in the same boat" makes no sense because no one knows what a boat is, either.