Life in the village of Poplar Springs is quite ordinary for 13-year-old Theodore Robins...until he and his older sister, Nelly, witness a strange event: a large, black dragon flies overhead and disappears behind the Queen's palace walls. A dragon hasn't been spotted in years, and for Theodore, it's his first time seeing one.

This sighting, along with his father's mysterious past and a bad omen from a scary old woman, make Theodore feel something is awry. His suspicions are confirmed when the Queen announces her intent to sacrifice a maiden to this black dragon, and the maiden chosen, to Theodore's horror, is his sister.

He and his mother are imprisoned, and Nelly now has only three days left to live. Can Theodore escape the Queen's dungeon and find a way to save her? Or will everything–and everyone–he loves, perish?