Fluttershy and Rainbow Dash are caught in a powerful storm near the Everfree Forest. They run to take cover in Fluttershy's cottage, but, during the trip, a large branch nearly kills Fluttershy. Rainbow Dash, despite being badly injured herself, takes it upon herself to get Fluttershy to safety and care for her until the storm passes.
(Added 6/30/13: an early effort of mine I was reminded of when someone favorite it, which is why you're getting notification spam about it now. My writing style has changed a lot since this story was written)