The story is set a full year after the fateful 'death' of Captain America in "The First Avenger". Carter is sent off to another military branch where she's brought down to being a desk worker. She then decides to prove that she's worthy to be a field operative once more which leads to the things you'll be seeing on the clip below. The one shot will appear with the Bluray version of Iron Man 3 among other things. Here's the clip from that MARVEL ONE SHOT.
