“The Battle of the Labyrinth, the fourth book in Rick Riordan's Percy Jackson and the Olympians series, follows Percy Jackson and his friends on a quest through the Labyrinth to stop Kronos' army from invading Camp Half-Blood. As war between the Olympians and Titans looms, Percy and Annabeth discover the Labyrinth's role in Kronos' plot and lead a group into the dangerous underground world” —Goodreads