Two percent of the world’s population disappeared on October 14,2011. That's the plot of The Leftovers. So where did they go? The cause of the Sudden Departure was never the point of Damon Lindelof and Tom Perrotta’s meditation on faith and grief, nor was the destination of those who seemingly vanished from existence. Nevertheless, and the series finale does go some way to reply the latter. One characters experience could either reveal a number of answers or simply lead you further down the rabbit gap.
Source: blastr.com