Smallville Season 6 episode 22

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i only watch ep 1 and 2 of season 6 and then i haven't seen any of smallville till last week. because it would be too much trouble to download from ep 3 onward i chose to watch from ep 19. i more or less can guess what happen from this few episode i watch. but naturally there some thing i don't understand happen in ep 22. how can chloe revive louis? some kind of experiment lex done to her? or a side effect of hanging too much around kryptonite?