Percy was training. In the sword fighting arena, just as usual. He had come here to think for as long as he could remember, and, boy, did he have a lot to think about. He hit the dummy on the neck and stopped and breathed for a couple of seconds. Only then did Percy realize how tired he was and almost collapsed. He stood up, put the cap on the end of riptide and turned around to go take shower and stopped in his tracks.
There was a girl standing just outside the arena staring at Percy. She was at least ten years younger than Percy probably younger and she looked Indian, which was odd because Percy had never seen an actually Indian person at camp. He guessed that the center of western civilization was not India, but here was this girl.
Percy had seen his fair share of new campers and he could tell from her aura of nervousness and confusion that she was one, so he composed himself and approached her.
"Hey," started Percy, "are you okay, do you know what... do you know what's this all is" he gestured around at the camp. The girl, now that Percy was closer he guessed was about twelve, looked extremely confused about what he was saying. He assumed that she got into camp alright but someone had forgotten to explain everything to her, its happened before.
"Well, do you know both of your parents," Percy asked, and the girl remained silent staring at him. Percy was silent for a few seconds deciding how to explain this particular situation to a girl that was refusing to talk. "Well, one of your parents is a god." Percy paused for the usual 'that's impossible' or 'you're lying' but the child kept her oath of silence, "like a Greek god, from mythology." Percy went on to explain everything to the girl who did not interrupt once. She took a deep breath and said "I knew both my parents and neither of them were Greek gods". "They were demigods, like you.