Sirius writes to James from Azkaban
I'm looking for a very short, deeply sad fic in the format of a letter written by Sirius in Azkaban to James on what would have been his 22nd birthday. This may have been one of the most beautiful, sad things I've read in my life, and I want to find it again. I don't even remember if there was implied R/S, but since that's most of what I read, there's a good chance of it. I'm probably using way more tags than necessary for this request, but I really want to find it, and I want other people to be able to find it, too, since it was amazing. I can't believe there's no tag for Azkaban fics.