The Battle of the Labyrinth
By Rick RiordanWhen the mysterious Labyrinth opens up, Percy is sent on a quest with his friends Annabeth and Grover to discover the secrets of the Labyrinth. They also seek to find anything they can use to protect Camp Half Blood from Kronos’ army. As they search, they work to discover Ariadne’s string, which is said to be able to guide anyone through the Labyrinth.