The Daughter of Poseidon

Percy Jackson has been through it all. From fighting monsters, to saving the world. There shouldn't be anything he hasn't seen. Until he meets his little sister. Alika Kayan is thirteen years old and has been on her own since she was ten.
His father orders him to go find her and bring her back to camp to keep her safe. But another force is at play, and Alika will not live for long if this force wins out. Will Percy be able to handle losing his closest relative; forever?