Originally Posted by ratbastid

The real puzzle is: some time between Seasons 2 and 3, Kate, Jack and Sawyer traveled between two different islands. How did they do that without knowing it? They didn't take the boat--Michael and Walt chugged off in that sucker, leaving the Others and the captured Losties on foot. So how'd they walk to the second island?

The answer is obvious: the Hydra station connects the two islands. Still, you'd think they would have gotten suspicious, walking through a long tunnel.