Darkness in Ember is helpful in hiding secrets. The secret room of horded treasures is down a dark hall in the Pipeworks, where Doon can only feel (not see) the key on the day he opens the door. The lights go out each night in Ember, creating an artificial nighttime so completely dark that everyone must be home by 9 pm. Doon is alone with his secret thoughts in the dark on the night before he plans to share the truth about the egress, and having to keep the secret makes him sleepless. Lina considers shouting the truth into the blackout from the top of the Gathering Hall at the Singing, but she cannot bring herself to release the secret into the dark. Also during that blackout, Doon realizes his own game-changing secret: “He had what no citizen of Ember had ever had before—a way to see in the dark” (229).

If darkness is a symbol for secrets in The City of Ember, natural light symbolizes revelations, inspirations, and truth. Here, the candles and matches stand as the strongest symbols; Lina and Doon expand their knowledge on several levels as they puzzle out how the candles and matches work. First, they figure out how to work the candles and matches to produce light by which to see.