It has been a month or two since the four humans arrived in Equestria and saved it. For Cale, a few nights has passed since his encounter with an entity from Princess Luna/Nightmare Moon's nightmare. Now they're about to face new enemies. Four to be exact, each one... An entity in the form of the humans' fears.

If you read this, I'll be assuming that you've read

The Four Horsemen of Equestria (First)
A Nightmare's Nightmare (Second)

Read those first before this one.