In the breathtaking conclusion to the Keeper of the Emerald trilogy, Emily and her friends are now involved in their most dangerous adventure yet. Emily is faced with the troublesome decision of whether or not she should use her emerald to help a young girl who has been abducted. In addition, Emily and her friends face a school shooting. Amidst these problems, Emily learns of a mystical ancient world where no human has ever set foot before. After traveling to this world, one of Emily's closest friends disappears in a mysterious jungle. In their action-packed attempt to find this friend, they encounter a tribe known as the Forgotten People who live in an underground network of caves and tunnels. The Forgotten People help Emily to discover a secret that puts every life on Earth in jeopardy. As one of Emily's closest friends turns against her, Emily must decide whether she is willing to sacrifice her own life to save the lives of others. Can Emily and her friends successfully complete one final mission? For Emily, this will be her final quest.