After Star Swirl the Bearded, Celestia, and Luna left the Disc, Rincewind has found himself at loose ends. Until, that is, the day a wizard of unusual gender informs him that all of reality is at stake. Now he knows what to run from, at least.
Newly-made alicorn Twilight Sparkle and her Number One Assistant have quite the brain-teaser on their hooves. Actually, they have several, since the citizens of Ponyville are plagued with riddles and puzzles lately.