This is an episode from the final season. We now know that the "Flash-Sideways" world is actually some kind of purgatory until all the castaways remembered what happened to them. Anyhoo, any Desmond Hume episode is guaranteed to blow your mind, leaving you drooling until the next day. He's dealt with time travel within himself and now his enemy/father-in-law Charles Widmore knows how special he is to the Island. Apparently, Desmond is able to withstand vast amounts of electromagnetic energy and still survive. The scene where he's forced into that chamber reminds me of the Watchmen comic and the origin of Dr. Manhattan. I used a picture from the movie to demonstrate. The top pic is from the Lost episode.
I found this great picture somebody made on Flickr of a young Charles Widmore and it cracked me up!!! I can't post it but please take a look!!