Leena al-Qasem pleaded with her son to leave the terror group. Instead, he murdered her in the heart of its savage capital city, before a crowd of hundreds. She was simply trying to save the life of her child. Instead, she fell victim to the first rule of any successful cult: Turn your followers against their friends, their family, and most importantly their parents. This being one of the most destructive cults in history—Leena, 45, was not simply cut off when she suggested escaping from the self-declared Islamic State; she was gunned down by her own son.