A new prophecy leads to a dangerous quest. When Percy receives an urgent distress call from Grover, he immediately prepares for battle. He knows he'll need his powerful demigod allies, Annabeth and Thalia, at his side; his trusty bronze sword, Riptide; and...a ride from his mom. The demigods race to the rescue, only to find that Grover has made an important discovery: two new powerful half-bloods, whose parentage is unknown. But that's not all that...

While the Olympians struggle to contain the rampaging monster Typhon, Kronos begins his advance on New York City, where Mount Olympus stands virtually unguarded. Now it's up to Percy Jackson and an army of young demigods to stop the Lord of Time.

Percy is confused. When he awoke after his long sleep, he didn't know much more than his name. His brain-fuzz is lingering, even after the wolf Lupa told him he is a demigod and trained him to fight. Somehow Percy manages to make it to the camp for half-bloods, despite the fact that he had to continually kill monsters that, annoyingly, would not stay dead. But the camp doesn't ring any bells with him. Hazel is supposed to be dead. When she lived before,...