Inkscape is a unicorn from Canterlot. She writes for a living, and usually enjoys her work, but the publishers are really laying it on hard, asking her to change her writing style to reach a wider market. With a little help from her agent, Critical Eye, she manages to get some time away in Ponyville to re-find her inspiration and rid herself of the worst case of writer's block she's ever experienced. However, she may have stumbled into more than she bargained for, when she ends up lodging in the spare room of Princess Twilight's library. She is quickly noticed by Twilight's friends, and given a traditional Pinkie Pie Welcome.
But the summer grows warm, even at night, the heat is sweltering, as if the sun never sets. Twilight, ever studious, hits the books, and discovers an ancient magic, older than the Princess Sisters themselves, that now threatens to overthrow the Equestrian Empire. Slowly rooting itself in the Equestrian leader, Celestia finds herself in danger.
The Mane Six leap into action, but could a normal unicorn writer do anything to help her new friends, or will she just have to sit on the sidelines and be forced to watch the world burn?