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).
Answer: According to Jack in season 5, Nina was "deep cover" before the pair ever met, so it's safe to assume she was recruited before she joined CTU. As for what her primary mission was, who knows? Perhaps it was to gather sensitive intel and pass it on to her superiors. Given that she worked for an intelligence agency, it's not a stretch. Or perhaps we may find out in season seven.
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