In this fourth installment of the blockbuster series, time is running out as war between the Olympians and the evil Titan lord Kronos draws near. Even the safe haven of Camp Half Blood grows more vulnerable by the minute as Kronos's army prepares to invade its once impenetrable borders. To stop them, Percy and his demigod friends will set out on a quest through the Labyrinth-a sprawling underground world with stunning surprises at every turn. Full of humor, heart-pounding action, and stunning illustrations, this thrilling adventure is a must-read for Percy fans!