What an excellent fic! I really liked the idea of the castle having a personality of its own and that it both protected and incarcerated Severus for his wrongdoings. Binns was refreshing - we hardly see him much in fan fiction and you made excellent use of him, both in his knowledge of history and in his special tie to the castle. I enjoyed the mystery and found myself getting anxious along with Harry as he paced and cajoled and worked tirelessly to find an answer.