This show follows a man who was involved in a car crash in which one of his loved ones died, but he doesn't know which one; when he goes to sleep at night, he seemingly switches realities, one in which his wife survived the crash and one in which his son did.
The main mystery is trying to determine which of these is reality and which is a dream, but as the series unfolds it becomes unclear if that's the right question at all.
The main actor (Jason Isaacs) has been great in everything he's acted in and he also produced the series.
It's a great blend of sci-fi and cop drama, kindof like Fringe I guess but I like it much more.

IMDB