I did a marathon Monday of the 5 episodes, and since it's Wednesday, here's my thoughts on how these 5 episodes may give a clue as to what we should see tomorrow night.
Before I get there, in case you missed it, Darlton told us to watch 5 episodes leading up to the S4 finale, indicating that's where the clues are buried. The 5 are...
Pilot Season 1
White Rabbit Season 1
Live Together, Die Alone Season 2
Through the Looking Glass Season 3
The Shape of Things to Come Season 4
So what's the common theme in all these? I found 2.
1 - Drugs and Alcohol
Probably a minor part, but Jack drank on the plane, got extra alcohol, used it as an antiseptic, Charlie and the heroin, Christian being on a binge according to the hotel guy, Des being a sod at the beginning of LTDA, Jack on a binge in TTLG, and Widdy and the bottle of Scotch on the nightstand.
How does that become a clue? I dunno, and somewhat doubt that it does. If I had to fathom a guess it would be how abuse of that separates you from the ones you care about...and from finding what you are really looking for.
Which leads me to #2
2 - Do you do things by yourself or do you depend on others
In LTDA Penny in her letter to Des said something like you just need to find 1 thing in this world...or maybe it was person...to find meaning. Des had his one thing in Penny. Jack had his one thing in fixing things. Kate finds her one thing in raising Aaron. Locke......hmmmmm.
I know people will say Locke's one thing is protecting the island, but I disagree. Ben's thing was protecting the island, but it wasn't his key thing as we saw when Keady shot Alex. The island is all Locke has. He has no family, no one he cares about anymore...no constant.
So to me this is the clue. Locke cannot do this alone, but he's going to anyway. He will turn his back on logic, reason, and rely singularly on faith.
I've argued since last year's Room 23 watchback that Locke was misguided, easily conned/coerced. I think rely solely of faith is misguided. I also think to a degree that may add to the political statement noted by Assuello...I think it was him...a few weeks ago. And I think the booze thing with Jack will play into this idea as well.
So the main clue we should see in the S4 finale is this. You can't find what you need if you separate yourself.
If you do not live together, you will die alone.