This story is a sequel to Hell On Earth
Takes place directly after the events of Legend of Everfree and is a prequel to "Hell On Earth". In terms of what order you read them in is entirely up to you (If you read both stories that is).
After everything that went on at Camp Everfree, Twilight has finally come home and now she can rest easy without any worry of magical demons like Midnight Sparkle.
Until she's suddenly awakened by none other than Midnight Sparkle. Though, something's different about her. She seems... less threatening and more annoying.