In the celestial library above the mortal world, a small angel named Mariel has spent her entire life reading. The library is vast and she has worked through almost all of it. One day she finds a book whose cover bears only the word Abyss — a name she has heard the elder angels speak of in careful tones. The pages inside are blank. The name refers to the world below the heavens, a place no one has told her much about. Her curiosity, once it takes hold, does not let go. She makes her way to the heavenly bridge and leans over the edge to see for herself.