Hi, so I'm a first time poster here so let me know if I've messed something up :)

I read a story, pretty sure I read it on Fanfiction.net, a looong time ago. John, Dean and sam (story focuses mainly on John and Dean) are hunting a shape shifter in the form of Mary Winchester. John and Dean chase her and corner her. They have a little argument and take focus off the shape shifter who takes advantage and grabs Dean and tries to use him as a hostage to get away. Sam comes in around this point, I can't really remember all that happens after. It's not a long fic but it's a good one. Not sure if it still exists anymore.

Any help is appreciated and thanks in advance :)