In the breathtaking fifth and final book in Rick Riordan's #1 best-selling Heroes of Olympus series; the Greek and Roman demigods must simultaneously prevent Gaea from waking and stop war from breaking out at Camp Half-Blood. Though the Greek and Roman crewmembers of the Argo II have made progress in their many quests; they still seem no closer to defeating the earth mother; Gaea. Her giants have risen-all of them-and they're stronger than ever. They must be stopped before the Feast of Spes; when Gaea plans to have two demigods sacrificed in Athens. She needs their blood-the blood of Olympus-in order to wake. The demigods are having more frequent visions of a terrible battle at Camp Half-Blood. The Roman legion from Camp Jupiter; led by Octavian; is almost within striking distance. Though it is tempting to take the Athena Parthenos to Athens to use as a secret weapon; the friends know that the huge statue belongs back on Long Island; where it might be able to stop a war between the two camps. The Athena Parthenos will go west; the Argo II will go east. The gods; still suffering from multiple personality disorder; are useless. How can a handful of young demigods hope to persevere against Gaea's army of powerful giants? As dangerous as it is to head to Athens; they have no other option. They have sacrificed too much already. And if Gaea wakes; it is game over.