When you first go into the court house and defeat twoface you hear a mans voice coming from the holding cells . He goes on to say something about visiting him on halloween ? Is there something i miss or do i have to visit this man on halloween .
he is downstairs and you have to visit him 12 times throughout the year. next day is halloween. if you check downstairs there is a calander on his wall with circled dates that you have to visit him on. Achievement will then unlcok.