The Diamond of Darkhold

The principal architect of the City of Ember prepares a gift for the residents of City of Ember who could one day return to the ground, but two hundred years has passed, that secret chamber has become dust-laden history that nobody knows. Lina and Doon find from a treasure hunter a torn-up book with missing pages, and Doon therefore produces a strong desire to go back to the underground City of Ember, so they embark on a new adventure.