The Battle of the Labyrinth is the fourth book in the Percy Jackson and the Olympians series, in which Percy Jackson and his friends Annabeth, Grover, and Tyson must journey through the Labyrinth to stop Kronos's army from invading Camp Half-Blood. The demigods search for the maze's creator, Daedalus, while navigating the ever-shifting and dangerous underground world, encountering monsters, and dealing with the growing war between the gods and Titans.