Camp half-blood is in chaos. Camp Jupiter just can't think straight anymore. Why? Because the only demigod son of Hades, Nico Di Angelo, is missing. No one knows where he went, why or how but they are determined to find him. The only person who seems to have an idea of his whereabouts is Hades but he has locked up the underworld and refuses to tell our heroes anything. Nico's sister Hazel is frantic and his boyfriend Will is worried out of his mind. But Hades can't throw the rest of the gang into this mess. No, it would be better if his son Nico does this on his own.