This story is a sequel to The Mane Six Regret Playing Truth or Dare
The first time the Mane Six played Truth or Dare, Rainbow Dash threw Fluttershy into the portal to the other world. She came out and said, "What happens at the Lit Club stays in the Lit Club." However, Rainbow wants answers. One day, Rainbow Dash and Twilight demand an answer from Fluttershy. She invites them over for tea and cookies, and explains what happened on the other side of the mirror portal. Fluttershy's story will leave Twilight and Rainbow speechless.
Reading the first story is not required, but recommended, especially if you would like to read about more shenanigans.