Juliet ambushes Jack as he's coming out of the shower

Juliet bursts into the Dharma house where Miles is keeping Hurley and Jack. Hurley and Miles are playing dominoes at the table and Juliet asks where Jack is. Miles says he's in the shower and Juliet asks if they can have some privacy. Miles and Hurley hop up and as they're walking outside, Miles asks Hurley to ask him more about time travel.

As Jack steps out of the shower, he's shocked to find Juliet standing with her back to the door looking very pissed. Juliet tells Jack that she needed his help with Ben. Jack responds with "That kid's Ben." Juliet says "It's not Ben yet, he's just a kid." Juliet makes it clear that she's not asking for his help now because he's made it clear that he's not interested. She tells him that Kate and Sawyer have go to try to help because they actually care. Jack tells her that he came back to the island because he cares and to save her and the others. Juliet yells at him "We didn't need saving!" She tells him that they've been fine for three years and that he came back for himself. Jack tells her that he came back because he was supposed to but he doesn't know what he supposed to do yet. Juliet tells him that he better figure it out.

So what is Jack's purpose? Right now he's just being obnoxious which he's been good at for a while now.