Percy has a scar on his hand, proof of Luke's betrayal. It's not very big and at first glance you do not even realize it's a scar. But there he is, reminding him that someone he really cared for that had betrayed him.
It is usually noticed only by people who know what happened (Clarisse, Annabeth, Grover, the Stoll brothers) and when they see it they give it a look full of sorrow (pity).
Percy tries to ignore them, because neither is such an ugly scar nor was it so terrible what happened.
There is another scar, even bigger but nobody sees. Only Percy knows he exists and tries not to think about it.
It's in his heart, because when Luke left it broke it into a thousand pieces. He was not just a friend, he was the first person he had loved. sorry its short im writing a long one which is tacking the mick oh and hi gay cable ;p
