Cronos has gathered a vast army of titans and plans to seize and destroy the sacred Olympus. To help him, he summons a powerful giant named Typhon. The gods go into battle against this dreadful enemy, leaving their home undefended. Only Percy Jackson and his half-blood friends recognize Cronos’s military trick and decide to stand guard for Olympus. They hope to repel attacks from monsters—or they will have to die in an unequal battle. Their hopes rest solely on a miracle and on help from those gods who are not yet taking part in the fight.