It's been a few years after Princess Twilight Sparkle's last encounter with the Doctor, back when she was just a pensive unicorn. During a peaceful night, a familiar blue box unexpectedly appeared outside of her own kingdom. Since she never saw her alien friend in such a long time, Princess Twilight enters the blue box, only to find nopony inside it.

The Doctor is missing and the only way Princess Twilight can find him is to read the diary that records the Doctor's every past exploits, companions, good times, bad times and all his different faces…