The end of the 1800s. A girl named Wisteria is peddling wares. She lives in the attic of a church and her only joy in life is the fact that the demon Marbas comes to visit her if she knocks on the far most window three times.

Marbas and Wisteria have forged a pact to be together, but the world doesn't take too kindly to dealing with demons, and now a familiar knight from the Sword Cross order is tracking them down.

Naberius goes berserk after Diana is shot, and it's up to Wisteria and Marbas to stop the rampaging great demon.