From Wiki: The Leftovers starts three years after a global event called the "Sudden Departure", the inexplicable, simultaneous disappearance of 140 million people, 2% of the world's population, on October 14, 2011. Following that event, mainstream religions declined, and a number of cults emerged, most notably the Guilty Remnant.
The story focuses primarily on the Garvey family and their acquaintances in the fictional town of Mapleton, New York. Kevin Garvey is the Chief of Police. His wife Laurie has joined the Guilty Remnant. Their son Tommy has left home for college, and their daughter Jill is acting out. The second season moves the main characters to the fictional town of Jarden, Texas.
The third season begins in Texas, but the main characters are moving to Australia, as evidenced in this teaser clip.
I wasn't for sure if I was going to like this show, at first thinking it was going to be some sort of rehash of the Left Behind series of books and movies, but it soon became clear that while there are religious overtones, they're subtle and the main religion is the cult, the (extremely creepy!) Guilty Remnant.
As is the case with many TV shows and particularly movies, the soundtrack adds significantly to the mood. The first season used The Leftovers Piano Theme - Max Richter for the intro and variations are played prominently throughout the episodes. The second season's intro was one of my favorite tunes, Let The Mystery Be by Iris DeMent. (Opening credits for the 2nd season) I'm not only looking forward to this finale season, but also to hear what new music they use. Another teaser clip has ABBA's "SOS" - my favorite tune of the Swedish group. A pop tune, sure, but seems to fit perfectly, same for the Richter piece composed for the series and DeMent's not-quite-religious (perhaps even Agnostic) ballad.
IMDb entry for The Leftovers
Official website (HBO)