Looking for a particular death story which I only heard a bit but haven't had a chance to read. 

In this fic, Dean was dead(killed?) and became some vengeful spirit. Sam heard about the spirit and went to hunt. I think Sam didn't know Dean was dead when gone to hunt. At the end, Dean thanked Sam for saving him.

I'm afraid that's all I remembered and I think it's sort of old story(around S3 or 4?).


Any help of suggestion would be appreciated!