Cutie mark crusaders, at the age of 8, begin to develop skills beyond the reach of any pony. Their strength increases dramatically, their hearing is now sharper than ever, and it seems they can no longer be damaged. This leads them to discover a secret that their families have hidden from them, they are not ordinary fillies, in fact, they were not even born as such. The very essence of the Tree of Harmony and the mysterious Chemical X runs in their veins, and it is up to them to decide what to do with these revelations.