The Doctor, Twilight, and Derpy arrive in the England of the Doctor's universe on Christmas Eve of 2010. What waits for them includes an icy storm, something from Derpy's past, and a reunion with a lost friend.
The Doctor and his companions accidentally travel to the year 56, where Equestria is currently at war with the new Changeling Empire. In order to stop the invading army, the Doctor will need to team up with a hardened Celestia and a simple farmmare.
Derpy wishes to go somewhere relaxing. The Doctor is willing to grant her wish but the unexpected appearance of a unicorn named Twilight Sparkle and the TARDIS unexpectedly taking them 600 years into the future changes his plans.
The Doctor finds himself stuck in prison, unable to remember anything he had experienced prior to his awakening. With the help of his diary, enchanted with magic, he tries to piece his life back together, not knowing what might await him at the end.
When Derpy finds a strange cylinder stuck in a tree, it's up to her to find out what it means. With some help from The Doctor, of course. He goes about and saves the town, again.