"Kate," Jack's voice was intruding into her silence, threatening to break her vigil. She was watching the waves, the same way she did every day, listening to the whispers in the ripples before they broke against the shore. She wasn't sure why she did it, only that it was necessary.
Jack's voice came again, more insistent, more demanding. Still she ignored him. What was the point in responding? The Kate he was calling for didn't exist, she was a sham, an illusion put up to protect a broken little girl. Kate was one of many disguises, and on the deserted island it had been the one that had fit best, slipping over her skin with so little effort that by losing herself in the thrumming heartbeat of the waves she could almost believe that she was real.
Her real name was Kathryn, but when she was five she had hidden herself behind Katie, the confident, pretty girl. She liked Katie. Katie would take all the hurt and hide it away, but she wasn't good at putting on the disguises then, and Wayne could cut through them. Katie had died with Wayne, leaving Kathryn to face her mom and Tom alone. With no one to carry the pain and the guilt away, she was left to wallow in her own agony, drowning slowly in a misery she had no way of dealing with.
She survived through pretending, making herself into someone she wasn't. This gave her a strange feeling of power, she was able to pretend that she was in control, not only of her own life, but of all these other people's too. The characters she had created had grown more extravagant, more untouchable. But then Tom died, and everything she had done seemed so ridiculous. She was a silly little girl playing with people's lives, and in the process she had killed the man that she loved. But by then she couldn't be stopped, her mind wasn't able to cope without the protection that peering at life through someone else's eyes gave her, and so she ran, creating new defences and new personas to hide behind with every step.
When Jack reached her, slightly worried about her lack of response, his voice was soft and soothing. It made her want to cry as much as it made her smile. She wonders if he knows that Kate can't be fixed, that she doesn't really exist. Kathryn wants to yell at him, to tell him to stop trying, to tell him everything and anything if he'll just stop trying. She's played with people's lives before and she's doing it again; she knows what will happen, she can see it playing out before her eyes. But she can't stop, Kate won't let her, and without Kate she's just a terrified little girl. With one last, wistful look at the waves, Kathryn abandons herself to Kate and follows Jack down the beach.