When monster attacks become more frequent, an demigods go spontaneously missing. That's weird. When Percy discovers that he has, not one, but two new siblings That's weird. When Percy's younger sister delivers a prophesy in a oracle-free world, that foretells Percy's future. That's really weird. Some time after the second giant war, defeat of Gaea and fulfilment of the Great prophesy, Percy and Annabeth are living the life; Until the arrival of two new siblings, which begins a snowball of trouble and worries for the simple life the couple planned out. Well, being a demigod does have some drawbacks.