Special Report: As Egypt's Brotherhood retreats, risk of extremism rises --- (Reuters) - In Egypt's second city, medical student Ahmed Nabil lives in fear that the police may come and arrest him any day. As a member of the Muslim Brotherhood, he is part of a movement facing an onslaught by the security forces which toppled Islamist President Mohamed Mursi in July. -- "These days we can be picked up at any time," said Nabil, whose parents are also members of the organization, Egypt's oldest Islamist movement and a supporter of Mursi.