Six years have passed since Diamond Tiara narrowly escaped the plants of the Equestrian desert. As her eighteenth autumn now sets in, she dedicates herself toward managing the fall Pony Prom, a celebration of her and all her school-friend's graduation.

What was supposed to be a fun time with her friends and coltfriend, however, begins to decay rapidly as Diamond Tiara begins to experience unusual symptoms. First came the headaches, and then the return of the voices- -and then the vision of strange, shadowy creatures infiltrating every space that she thought was safe.

As Diamond Tiara slowly slips into madness, new truths begin to form- -and she begins to see that what she thought was insanity might be a harbinger of something far more worse.