After a hectic time travel loop and saw the strangest things that she'll ever see, Twilight thought she can relax and show her new friend; Starlight Glimmer, around the castle. However, as they were taking the tour, Starlight notice one of the books were flashing. Soon, Twilight realize that her friends from another world was needing her help and try to call for her.
You can consider this to be a prequel to 2nd Weirdest Thing.