I love this! I don't know how I missed this, but I discovered it a week or so ago over on ff.net.
It is going to be my Tuesday rec this week for the LJ comm One_bad_man where I do a weekly rec. I love anything with SS/HG and of course you can't go wrong with cats. :) Severus' name for the kitten is perfect. Thanks for sharing.
Delightfully haunting at the beginning and perfectly sweet by the end. Well done!