Disclaimer: Harry Potter belongs to JKR, this is written for my own enjoyment. No copyright infringement is intended.
"He's at Hogwarts!"
It all started with a crossword puzzle. He had seen the picture. Now he knew that the rat was still alive, and he was at the castle. The rat was near Harry, and nothing could be done about it. He knew that he needed to get out, that he needed to protect Harry. It had never been done before, no one had ever escaped.
He had been able to keep his mind mostly intact. Most of the people who knew him would say he was halfway 'round the twist before his conviction anyway. It was ironic that by transforming into a dog, he was able to keep his mind human.
He had never questioned whether he belonged in Azkaban. He knew he had killed James and Lily, as sure as if he had aimed the wand himself. He had trusted the wrong person. He had based his mistrust on something that shouldn't have mattered, that had never mattered before.
If only he could prove that the rat was still alive, if he could redeem himself. He could begin to heal the scars that were growing deeper by the day.
A/N: a bunch of you suggested this person, I won't make a list, so as not to forget anyone.