This is a wonderful episode, through the flashforward we learn that Kate and Jack are a couple and that they also got engaged! Jack visits Hurley in the mendal clinic and Hurley says to him that he saw Charlie and he gave him a note to deliver to him. The note wrote "You are not supposed to raise him",and obviously he meant Aaron. In addition,we find out how Jack started to drink and became depressed. That's because his father's spirit (black smoke?) visits him and Jack starts taking pills to avoid seeing him. At the end of the flashforward, we see that his relationship with Kate starts changing, and it seems that they are going to break up.
On the island, Juliet has to remove Jack's appendix. Bernand and Kate help her as well.
Sawyer,Miles and Claire are on their way to the beach. However,during the night, Jack's/Claire's father appear and takes Claire somewhere with him. When Sawyer finds out about it the next morning, he starts looking for her and he finds Aaron alone in the jungle.
Great episode which prepares us for what's coming next!