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.

At the conclusion of The Mark of Athena, Annabeth and Percy tumble into a pit leading straight to the Underworld. The other five demigods have to put aside their grief and follow Percy's instructions to find the mortal side of the Doors of Death. If they can fight their way through the Gaea's forces, and Percy and Annabeth can survive the House of Hades, then the Seven will be able to seal the Doors both sides and prevent the giants from raising Gaea....

"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."-- "Cuando Jason despierta, sabe que algo va muy mal. Está en un autobús camino de un campamento para chicos problemáticos. Y le acompañan Piper --una muchacha (bastante guapa, por cierto) que dice que es su novia y el que...

"Uniting with Jason, Piper, and Leo after their dangerous quest, Percy, Hazel, and Frank wonder who will be chosen to fulfill the Prophecy of Seven, completing their group's number, and sail with them to an ancient land to find the mysterious Doors of Death."--

Athena and Hermes' search for the cause of their unexpected, life-threatening illnesses leads them to Cassandra, a former prophetess, who may be key to a war started by Hera and other Olympians who have become corrupt anti-gods determined to destroy their rivals.

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.

"Greek and Roman demigods from the Prophecy of Seven must work together to seal the Doors of Death, and help Percy and Annabeth escape the Underworld in the process." -- "Gaia, la madre tierra, se ha propuesto destruir el mundo de los mortales con sus tropas de monstruos y gigantes, y solo hay un modo de impedirlo: cerrar las Puertas de la Muerte, por donde estas criaturas están escapando de los infiernos. Y, lo más importante, hay que hacerlo...