Not sure why I've never added this one to the thread before as it's one of my all time favourites; a great enf blackmail story. I originally came across it on the old askjolene site and luckily it was stored elsewhere too. I won't spoil the story for you but here's the synopsis the author provides:
Synopsis: Sarah's younger sister takes some pictures of her in a compromising position and compels her to do some embarrassing things.
It can be found here in two parts:
http://www.bdsmlibrary.com/stories/s...p?storyid=5671
Enjoy!