Each time a young man leaves a quiet suburb to join ISIS, we are shocked. Why do they do it? How can they be stopped? And if they come back, what to do about them? These are the questions that drive Mubin Shaikh on his quest to stop potential jihadis. Mubin went from militant extremist to undercover operative. Now a Counter-Terrorism expert, he takes to the frontlines of the battle against violent extremism around the world.