The oracle of the half-blood field pronounces a terrible prophecy: "Seven half-bloods to the call will respond. Fire or storm The Cader world will do". A new group of heroes will face a dangerous mission: preventing Gea, the Mother Earth, awaken and, with the help of the giants, destroys the gods of Olympus and whole humanity. To do this they will have to move to Greece and go down to the abyss of the Tartar to close the doors of death: an arduous and frightening mission that can only be addressed if the Greek semiides of the half-ban and the Roman fields of the Campo Jupiter will decide to collaborate. But before the final battle the seven of the second great prophecy - Jason, Piper, Leo, Percy, Annabeth, Hazel and Frank - will have to overcome fearsome tests and fight harrowing enemies.