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.

Wisteria and Marbas encounter another young girl with a demon pact, who may not be exactly what she appears at first glance.

After Wisteria collapses in the snow, Marbas brings her to Blackbell manor to find Naberius and his contractor preparing for war.

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

As Wisteria and Marbas travel to the Lake District with Diana and Naberius, Snow has an encounter with some old friends that takes a dangerous turn.

Accepting Sitri's invitation, Wisteria and Marbas head to London hoping to rescue Snow.

With Wisteria exhausted from their arrival in London, Marbas searches for Snow. But is he too late?

Forced to confront the likelihood that Snow may have been lost forever, Wisteria and Marbas decide to search for him anyway, while the Commander of the Cross Sword Knights clashes with Dantalion and Luther.

The Commander of the Sword Cross Knights rushes back to headquarters, the rest of the order tries to contend with an assault by Dantalion and Luther.

Trapped in a torturous mental labyrinth by Sitri, Wisteria searches for a way to exorcise the demons possessing her brother.

Snow, freed from Sytry's grip, assists his sister and Marbas in their fierce fight against Luther and Dantalion, who unleash their fury. The little girl and her devil will do everything to stop them.