If you're the creators of Lost and you are looking for a sure-fire way to heat up the season, the answer is always the same. Dig up a John Locke episode. It works every single time.
Tonight's episode, "The Substitute" is proof of that, as it combined more honest suspense, emotion and intrigue than the last three episodes combined. It even managed to end on a note of near revelation. We may possibly know the impetus behind why all of the 815ers are really on this island.
That is, of course, if Smokey Locke can be trusted. While I sincerely doubt he can be, I also don't think he was lying to Sawyer in the cave when he revealed that Jacob had been looking for a replacement guardian for the island. A replacement to guard what? The creature disguised as Locke is my guess, but is it all bigger than that? Earlier, in the jungle with Sawyer, Anti-Locke said he had once been human too, and attempted to deceptively relate to the younger man's pain.
Read the rest of the Lost recap here.