Khara Chase is a daughter of Poseidon and adviser to the gods. She is "sisters" with Annabeth Chase. When I say sisters I mean Khara was adopted by Annabeths dad. They say they're twins because they look exactly alike (except for hair and eye color) and have the same birthday. What happens when Khara is ordered by her father to go to Camp Half-Blood and she gets sent on a quest after a certain camper goes missing? To find out you have to read for yourself.