When rummaging through Twilight's library, the Cutie Mark Crusaders find an old, torn up book, in it, lie the myths and secrets which have never been heard of before.
However, most of the pages from the book are missing, so they go to Twilight to ask for her help.
Twilight seems to know nothing about the book, and therefore asks her friends, who know nothing as well. With nopony left to turn to, she goes to her tutor, Princess Celestia.
Celestia seems to be evading her questions, making Twilight very suspicious.

An investigation begins, but some of the secrets were better off when nopony knew of them…