▁as ▁the ▁first ▁head ▁coun sel or ▁of ▁the ▁P ose id on ▁cabin ▁at ▁his ▁dem ig od ▁summer ▁camp ▁– ▁Camp ▁Half - B lo od . ▁ ▁After ▁The ▁Last ▁Olymp ian , ▁the ▁next ▁time ▁Per cy ▁is ▁seen ▁is ▁in ▁The ▁Son ▁of ▁Ne pt une , ▁the ▁second ▁book ▁in ▁the ▁sequ el ▁series ▁The ▁Hero es ▁of ▁Olymp us . ▁He ▁is ▁suffering ▁from ▁am nes ia ▁and ▁slowly ▁strugg les ▁to ▁reg ain ▁his ▁memory ▁over ▁the ▁course ▁of ▁the ▁novel . ▁For ▁a ▁while ▁in ▁the ▁book ▁he ▁cannot ▁remember ▁anything ▁other ▁than ▁An nab eth ▁Ch ase , ▁his ▁long - time ▁friend . ▁He ▁arriv es ▁at ▁a ▁Roman ▁establishment ▁called ▁Camp ▁Jup iter , ▁and ▁is ▁elected ▁pra et or ▁as ▁a ▁result ▁of ▁the ▁help ▁he ▁offers ▁them ▁on ▁a ▁quest . ▁During ▁the ▁remaining ▁three ▁books ▁in ▁the ▁third - person ▁his ▁character ▁develop s ▁significantly . ▁He ▁develop s ▁an ▁ir r ational ▁fear ▁of ▁d row ning ; ▁is ▁hum bled ▁by ▁weak ening ▁sword - f ight ing ▁skills ; ▁and ▁express es ▁a ▁new ▁t endency ▁to ▁make ▁ambigu ous ▁moral ▁choices ▁in ▁defense ▁of ▁his ▁friends ▁and ▁family . ▁One ▁of ▁the ▁character ' s ▁dark est ▁moments ▁comes ▁in ▁The ▁House ▁of ▁H ades , ▁when ▁Per cy ▁disco vers ▁that ▁he ▁can ▁control ▁the ▁water ▁in ▁a ▁person ' s ▁body , ▁and ▁uses ▁it ▁to ▁tort ure ▁the ▁god dess ▁Ak