He Was Innocent

"I knew only as well as you did-" the headmaster started. "I did know!" Remus yelled, anger and resentment bubbling up inside him. "Twelve years Sirius rotted in that prison surrounded by dementors! You were willing to give Severus bloody Snape a second chance and you saw the mark on his arm but not Sirius." The story of why Remus really resigned.