Ciel and Sebastian infiltrate the secret dungeon beneath the Emerald Castle, where they persuade Sullivan to explore the forbidden "outside world" with them. In the process, they discover an underground factory where the so-called "Miasma" – a deadly chemical weapon disguised as Sulin Gas – is being produced. The "Werewolves" turn out to be masked humans manipulating Sullivan to advance the gas production.

Sullivan's "Ultimate Magic Formula" proves to be the chemical formula for the gas, which they unknowingly developed on behalf of the Crone and the scientists disguised as werewolves. The Crone reveals that the gas is intended to be used as a weapon of mass destruction and proudly names it after Sullivan. Meanwhile, Ciel and Sebastian uncover that the "protective talismans" of the villagers are actually tracking devices monitoring their movements.

As Sullivan is confronted with the truth – that her role as the "Emerald Witch" is a lie to control the village – Diederich, an ally of the Phantomhive network, arrives and documents the factory.