Riordan: Heroes of Olympus: The Mark of Athena

In Son of Neptune, Percy, Hazel, and Frank met at Camp Jupiter, the Roman equivalent of Camp Half-Blood, and traveled to the land beyond the gods to complete a dangerous mission. The third book in the Heroes of Olympus series will reunite them with Jason, Piper, and Leo. But there are only six of them—who will complete the prophecy of seven? The Greek and Roman demigods will have to team up to defeat the Titans unleashed by Gaia, the Earth Mother. Then together they will sail to ancient Earth to find the Doors of Death. What exactly are the Doors of Death? Much of the prophecy remains mysterious... With the combined efforts of old and new friends, a magnificent ship, terrifying enemies, and an exotic setting, The Mark of Athena will be another unforgettable adventure from master storyteller Rick Riordan.