Plot

In the fourth Book of Ember, Things pick up from the end of Book 2. The Emberites are considered Sparks citizens. The day's work has ended, when suddenly Doon's Father trips and badly injures his hand on a pane of glass (he shattered it, of course). Later, a roamer comes to town, and Doon buys a book that has only 8 pages remaining. The cover of the book gives Doon the feeling that he should go back to Ember to search for items left behind. When he arrives with Lina, however, he is taken captive by The Troggs, who claimed Ember for their own, calling it Darkhold. Lina runs into Maggs, the roamer, Doon escapes, the Sparks citizens come to look for Doon and Lina, The two fight of a pack of wolves, and get home. But most importantly, When they return, they're carrying all the useful leftover items from Ember, an a new discovery, diamonds that make electricity, which Doon first discovered when Washton Trogg had one, although he didn't know what it was for. Hence, the title: The Diamond of Darkhold. I was not able to find a theme in the book, and I'm not sure there is one.