Due to the events of not only becoming an aunt and gaining a new student, Twilight realized that she hadn't spoken to her humanized friend, Sunset Shimmer, in quite a long time. So in an attempt to rectify this mistake on her part and hopefully mend any issues, she decided to enter the portal and spend time with the former student of Princess Celestia.

But what transpired as soon as she opened the portal gave the alicorn something dreadful to fear. And when she went through to the universe on the other side, she's confronted with an apocalyptic nightmare. Now she must find her friends and figure out how to survive in the land of the infected.