Day 4: 3:00 P.M.-4:00 P.M. - S4-E9
Continuity mistake: In the previous episode, when Jack and Tony try to stop the helicopter, they drive off the road and hit the front bumper and lose their front license plate. This is also visible in this episode as Jack and Tony wait for backup and when they drive off there is still no license plate, but about 8 minutes later, when they arrive, the license plate is back on. Since the show is in real time and they arrived in the exact time they said they would, they couldn't have stopped to get it fixed or anything.
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.
Cubs Fan ★