[1][2][3] The series follows two central characters, an astrophysicist (Bill Pullman) and a nun (Natascha McElhone), in a race against time to see if the end of the world can be averted.
Dr. Richard Massey, a noted astrophysicist from Harvard, returns home after having hunted down the Satanist that brutally murdered his daughter Lucy in a satanic ritual.
Meanwhile, a nun named Josepha Montafiore who is working for the Eklind Foundation, a wealthy traditionalist Catholic organization, visits the bedside of a comatose girl.
The girl's visions lead Josepha to Richard, who joins her on her quest to document and unravel signs of the End of Days.
Their journey eventually becomes a race against time to thwart Haden's followers as they try to bring about the Apocalypse, all while hot on the trail of a child who may be able to save them all.