Day 4: 12:00 A.M.-1:00 A.M. - S4-E18
Factual error: In the opening scene of the episode, Marwan gives a cohort Lat/Long coordinates for a nuclear missile. The computer shows these coordinates as being in the Midwest, they are actually in Nevada. (37 14' N 115 21' W).
Chosen answer: Nobody knew, not even the writers, until at least halfway through the season when they were writing the end. They wanted to keep all options open.
Nick N.