There has been a temporal tear and it is of course the Doctor's job to fix it. But it is far to dangerous to take his dear companion with him, and he must leaver her behind. But the due to the relativity of time, several years passed on his home world, while to him it's been only a few days. A war has broken out between Equestria and the Griffon Empire, and Ponyville is no longer. Derpy is no longer the pony she used to be. She hides her cutie mark and her bad eye, and has risen through the ranks as General Grey. But suddenly, the Doctor returns and that changes everything.