"Out There," by Zoe Beck, in Ellery Queen's Mystery Magazine, February 2012.
Among the other changes that e-mail has wrought in the world is an improvement in epistolary fiction. It is possible to exchange letters a lot faster than when DIego de San Pedro wrote the first epistolary novel in the fifteenth century.
And that's what German author Zoe Beck presents with, a story written entirely in e-mails. Most of them are written by Gil Peters, who is a successful author despite having agoraphobia so fierce that she hasn't left her apartment in eight years. But that's okay, she has adjusted to it, and with her computer and her shrink on tap she is doing fine.
Then her doctor goes on vacation just when an unacceptable change happens to her home. Things start to go rapidly out of hand...
The only thing I love better than a twist ending is multiple twists, and Beck provides them. I thought I knew where the story was going. Then I thought I saw the new direction. Nope. No wonder it won the Glauser prize.