The Mystery Hero

A new hero comes to halfblood hill with no memory of anything, but her name and a phrase. Just being at camp isn't safe anymore now that this new demigod is here. Trouble comes searching for her just as the new prophecy said it would. How can the demigods keep her safe and protect everyone at camp? How will they react when someone they knows comes back into the picture? And how will everyone act when they are betrayed as easily as you would drop any item you didn't want?