After helping Princess Luna reach out to the human fighters rejecting ponification on Earth, Rockheart the guardspony resumes his daily duties as a member of the Palace Watch, the earth-pony branch of the Royal Guard. Soon, however, the arrival of three visitors to the royal court will embroil him in larger tensions between Equestria and the remnants of the United States government, not to mention some unfinished business he's unknowingly left on Earth…

Part revenge story, part political thriller, Terminal Leave directly follows the events of Railroad Seven-Three.