Up until the literally explosive final two minutes of “A Flash of Light,” Homeland’s sixth season has taken a radically different approach to its narrative. Rather than dealing with an immediate threat, the series has revolved around the hypothetical threat of a nuclear attack, one that’s at worst still several years down the road. Instead of establishing an obvious villain, the series has criticized the F.B.I. for essentially inventing homegrown terrorists like Sekou Bah (J. Mallory McCree) and suggested that Mossad might also be fabricating threats with the use of false-flag operatives like Iranian moneyman Farhad Nafisi (Bernard White). The people doing all the threatening in this episode are the ones who’re supposed to be the good guys: the C.I.A.’s Dar Adal (F. Murray Abraham), casually accosting Carrie Matheson (Claire Danes) as she picks her daughter up from school, and the Israeli government’s Etai Luskin (Allan Corduner), politely detaining Saul Berenson (Mandy Patinkin) on his way back to America from the West Bank.