Annabeth has been away from Percy for six months, but at last she and he are about to be reunited. However, Annabeth fears Percy's time at Camp Jupiter may have turned him to the Roman ways instead of the Greek, and that he may no longer need her even if she needs him. Annabeth has been tasked by her mother, Athena, with following Athena's mark to get revenge on her mother's enemies--on top of Annabeth and the other demi-gods' task of fulfilling the prophecy and sealing the Doors of Death.
Demigod Percy Jackson, still with no memory, and his new friends from Camp Jupiter, Hazel and Frank, go on a quest to free Death, but their bigger task is to unite the Greek and Roman camps so that the Prophecy of Seven can be fulfilled.
Jason, Piper, and Leo, three students from a school for "bad kids," find themselves at Camp Half-Blood, where they learn that they are demigods and begin a quest to free Hera, who has been imprisoned by Mother Earth herself.
Hazel and her crew on the "Argo II" have a choice to make: to bring the statue of Athena Parthenos back in order to stop Camp Half-Blood and Camp Jupiter from warring with one another; or to sail on to find the House of Hades and attempt an impossible rescue of Percy and Annabeth from Tartarus. Meanwhile Annabeth and Percy are trying to find the Doors of Death from the other side of Tartarus in order to stop the vengeful Earth Mother Gaea from rising to power.
