It's been a long time since anyone saw anything like this. Terrorism is history. After the Middle East wars and the rising sea levels—after Armageddon and the Flood—came the Great Rejection. The first Enlightenment separated church from state. The Second Enlightenment has separated religion from politics. In this enlightened age there's no persecution, but the millions who still believe and worship are a marginal and mistrusted minority. Now someone is killing them.
At first, suspicion falls on atheists more militant than the secular authorities. But when the target list expands to include the godless, it becomes evident that something very old has risen from the ashes. Old and very, very dangerous.