It bothers Agent Sydney Bristow's conscience that too often her job asks her to work with criminals she would much rather put away. She understands the logic - the lesser of two evils approach is all too familiar to her - but that doesn't make it any easier to accept. Someone else disagrees. APO's more dubious contacts are being assassinated, with only a calling card depicting a black star with the number thirteen in its centre for a lead. When it becomes clear that a lethal, highly trained vigilante organisation is interfering with APO's missions, Sydney must put aside her empathy and help shut down these mysterious "13 Stars". But when Sydney herself is mistaken for a freelance terror agent, she worries that the mistake is not so far from the truth. And now that she's marked, both her cover and welfare are in immediate jeopardy...