Christian Shephard and Claire in Jacob's cabin!

Locke goes into Jacob's cabin to find Christian Shephard instead of Jacob. Christian can speak on Jacob's behalf. Both Christian and Locke know that Locke is there because he was chosen to be. Locke then turns and sees Claire sitting in a chair with a devilish grin on her face. She tells John that she's with Christian. Christian says that Aaron is where he needs to be which is not there. John is confused by Claire being there but Christian says there's no time for that. Christian knows the people on the boat are already on their way back and that Locke should ask the one question that does matter. Locke then asks, "How do I save the island?" Christian and Claire both look pleased.

This is possibly the best scene so far this season. The number of questions that arise from it are seemingly endless. Why is Claire there? Why does she look so devilish/sneaky? Why is Christian there and not Jacob? Is Christian Jacob? I could go on for days.