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I think that Jack may be freaking out so much because he now realizes that Locke was right when they were on the island. Locke said that they were meant to be there, while Jack didn't think so. Jack is a man of science and Locke is a man of faith. Now Jack realizes that Locke was right -- they were meant to be there.
It will be interesting to see Sawyer and Juliet's relationship since everyone on the island probably thinks that eveyrone on the frighter is dead. The only charachters we know, still on the island are Rose, Bernard, Juiet, Locke, Sawyer, Charlotte and Miles.