The Butler, In a Rage (その執事、狂暴, Sono Shitsuji, Kyōbō) is Chapter 99 of the Kuroshitsuji manga.
Summary[]
Sieglinde Sullivan eventually decides to venture into the outside world, when Ciel Phantomhive convinces her that she is capable of creating a magical, ultimate medicine to save lives.
Meanwhile, Sebastian Michaelis is facing off with his opponents, the men in werewolf costumes. Some of them hastily release mustard gas, in an attempt to suppress Sebastian, but to no avail. After Sebastian slaughters them, he finds the village crone, who is trying desperately to preserve the SuLIN samples and documents. The poisonous gas alarm goes off, due to Sebastian exhaling mustard gas. After disposing of her, Sebastian recalls that Ciel had ordered him to erase all the formulas of SuLIN created by Sieglinde; Ciel had also explicitly allowed Sebastian to employ whatever method he wants to achieve as such.
Sebastian lights the entire place on fire while commenting that what he deems most entertaining at the moment is playing the butler in his game with Ciel.
In the Werewolves' Forest, the Phantomhive servants unite with Ciel and Sieglinde. Ciel tells them to split into two groups and escape, signalling the commencement of their retreat plan.
The fire engulfing the B4 Factory under the Emerald Castle causes a huge pandemonium; the people at ground level are utterly startled. Hilde is informed that the gas samples have been stolen. Wolfram addresses Hilde as Major Hilde Dickhaut, and says that their priority should be to capture Sieglinde. First commando squad captain, Anne Drewanz, and second commando squad captain, Grete Hilbard, announce that they are ready for action. Anne states that they have located where the flare came from and that they are prepared to operate the new experimental weapon. When questioned, Hilde affirms to Wolfram that they will be using the new weapon. She changes into her military uniform and declares that while their primary goal is to retrieve Sieglinde, they are to kill her if she leaves the Werewolves' Forest.