Journeyman on NBC last year rose to the occasion once, in its splendid episode before the finale. Journeyman was a time travel series.
Lost was never really about time travel. But its Desmond story - a man who sees the future - certainly could have been a time travel story. I wrote in my reviews here last year that time travel might well explain what was going on with Desmond, and those he touched.
Tonight, in Episode 5, Lost took that path - or, actually, made good that path which it had already been on its way to building, from the time Desmond unaccountably ran into Jack on the steps of the stadium well before the flight of Oceanic 815, to the little experiment with time pieces we saw Faraday doing on the island a few weeks ago. Actually, Lost did better than make good - it made great, genius, golden television tonight. Great for the episode, great for the series.
Here, for what it's worth, is my take on what we learned in tonight's show. I'm sure there will be other explanations.
Let's think of the Desmond we saw before tonight's episode as Desmond 1 - with one exception which I'll get to, shortly. Desmond 1 breaks up with Penny. He travels around the world, sees Jack on the steps of the stadium (this is the exception to Desmond 1, as I'll explain below), winds up in the hatch on the island. He loves Penny now, and wants to get back to her. The hatch blows, exposing Desmond to intense radiation. He's still Desmond 1, but he begins to have visions of the future.
In one of the flashbacks last year, in Episode 3.8, Desmond has a conversation with Ms. Hawking (played by the always-memorable Fionnula Flanagan, also seen on Brotherhood). She apparently has knowledge of Desmond and his future which he and we did not yet have at the time of that episode. This was likely the second reference to Desmond 2 (and I'll get to the first in a few paragraphs).
Desmond 1 continues on the island, plays the crucial role in getting Charlie to the Looking Glass, etc. The last we see of Desmond 1 is when he is on board the helicopter with Sayid before it goes off course.
We learn tonight that electromagnetic fields do strange things to people's perception of time. The hatch explosion radiation gave Desmond visions of the future. The strange properties of space/time around the island - in part natural, in part the result of some technology - boost Desmond's temporal powers, to the point that his consciousness is able to instantly, uncontrollably travel through time.
This turns him into Desmond 2. This Desmond first emerges and travels from the helicopter off the island to Desmond 1 back in an army camp. But once the temporal connection is made between future Desmond 2 and past Desmond 1, the original Desmond - Desmond 1 - in that training camp becomes Desmond 2.
Desmond 2 in the past, informed by Desmond 2 in his future (our present - what we're seeing on our television screen) goes to see Faraday in Oxford, and Penny in London. The instant he sees them, and gives them any information from the future, they, too, are turned into Faraday 2 and Penny 2.
The heart-warming part of this story is that Penny 2 comes to serve as Desmond 2's "constant," and Desmond 2 comes to serve as Faraday's. This saves their lives. (As we learn from the unfortunate Minkowski, having your mind moving around in time can otherwise be fatal.)
And here's something else: I've long been citing Desmond's running into Jack on the steps, in the first episode of Season 2, as one of the inexplicable coincidences which may hold the keys to what is really going on in Lost. What are the odds of Desmond having run into Jack, before Desmond wound up in the hatch on an island on which Jack crashed?
All but nil.
But now we have a rational explanation. It was not coincidence. Desmond spoke to Jack the way he did on those steps, and went to meet him there in first place, because Desmond 2 needed to talk to Jack - Desmond 2, who of course already knew everything about Jack and the island, because Desmond 2 had lived through it. Just as Desmond 2 was in touch with his earlier self in the army camp, in Oxford, in London, tonight, so Desmond 2 was in touch with his earlier self before that meeting with Jack at the stadium.
And why did Desmond need to meet and speak to Jack?
Because Desmond 2 knew how crucial Jack would be in helping Desmond get off the island, and back in touch with Penny...
See also...
Further Questions about Lost 4.4: Jack and Aaron, Kate and Sawyer
1. Lost's Back Full Paradoxical Blast 4.1 ... 4.2: Five Flashbacks and Three Rational Explanations ... 4.3: Thirty Minutes and Big Ben ... 4.4 Kate and ... ... 4.6 The True Nature of Ben ... 4.7 Flash Both Ways ... 4.8 Michael and Alex ... 4.9 Daughters, Rules, and Some Truth about Ben ... 4.10: Almost a Dream Come True ... 4.11 Unlocking Locke
and
2. More Thoughts On Lost 4.1: Those Who Went with Hurley and Those Who Stayed with Jack and Two More Points about Lost 4.1
special 10-minute podcast of this Lost review and analysis
The Plot to Save Socrates
"a Da Vinci-esque thriller" - New York Daily News
"Sierra Waters is sexy as hell" - curled up with a good book
more about The Plot to Save Socrates and its time travel ...
Read the first chapter of The Plot to Save Socrates .... FREE!
"Ain't you the King of Diamonds," Bunk sarcastically remarks to McNulty, as McNulty hands out resources to a revitalized Baltimore police - revitalized because McNulty's charade about a serial killer of homeless people has galvanized everyone from the Mayor on down. No "weak shit" this, as Bunk termed this a just a week or two ago.
And State Senator Clay Davis (finely played by Isiah Whitlock, Jr.) won his case! 
