At first, Peter Driscal doesn't appear as a fully-formed character. Because we're in Cole's head throughout the book, we see Peter through Cole's eyes—as an unimportant person who happens to be the victim of Cole's latest crime. Even though Peter might suffer from permanent damage and is obviously very hurt and traumatized from the experience, Cole dismisses his pain and sees him as someone who brought everything upon himself because he's weak:
Cole studied Peter. Peter hadn't sounded like this before. Cole wiped his sweaty hands on his pants. It wasn't like he had meant to hurt anyone. Besides, this wouldn't have happened if Peter had kept his mouth shut. (4.44)
Poor Peter is suffering from a lot of pain and trauma from Cole's attack, and he has to be there to see Cole through all of his sentencing details. He has to constantly come into contact with his attacker again. Ugh.
Although Cole initially assumes that Peter will heal and get over what happened, he soon realizes he's done a lot more damage than he thought. Even after Peter starts to heal physically, he continues to get worse and worse emotionally. When Cole learns that Peter has tried to commit suicide, he is horrified and feels super guilty. He decides Peter should come to the island so Cole can help him heal and move on:
Edwin picked at the rough edge of the table with his thick chipped thumbnail. "Peter tried again last night to commit suicide. His parents are desperate." Edwin placed both hands flat on the table. "Yesterday, when I left here, you said that you could help Peter. And you hollered after me that I wasn't listening. Well, now I'm listening. Tell me what you meant." (24.64)
When Peter comes to the island, Cole can see firsthand just how damaged the boy is. He's filled with anger and pain, and he doesn't know what else to do besides lash out at Cole. Over time, however, Peter's invisible emotional scars start to heal, and by the end, he's even hanging out with Cole and teaching him how to carve:
Peter shrugged awkwardly and grinned at Cole. "A circle is all I could teach him to carve."
Cole smiled and nodded. "I'm a slow learner. But I'm working on it." (28.75-76)
Cole isn't the only one who undergoes a critical transformation from being on the island. Peter changes for the better, too…though the only reason he has to heal in the first place is thanks to Cole.