Just watched 5th Episode and it was the best ever, IMHO. Desmond races against time to find Penny in 1996 and their love for each other make the best episodes. This dram series is full of cultural references, physics, time travel and all other mind blowing stuff. Desmond realizes that he is caught in a some kind of time warp that is toggling his consciousness between two different bodies at two different points in time and space. I don’t wanna talk about what Daniel Faraday had in his journal, especially a page that reads: “If anything goes wrong, Desmond Hume will be my constant.”; fantastic stuff :)
As usual, Lostpedia has all the details about 5th episode.