Lord El-Melloi II recibe un encargo de su hermana para ir a visitar a una de sus antiguas alumnas y ayudarle a resolver el misterio del asesinato de su padre, una labor en la que muchos magos ya se rindieron.

Cuando Lord el Melloi descubre que su cafetería favorita tiene que cerrar por un problema con ratones, ocurren dos cosas. La primera es que pierde los papeles con mayor facilidad. La segunda es que decide ponerse en marcha él mismo e investigar el caso, que irá más allá de unos simples roedores.

La muerte del padre de Wills, viejo conocido de Lord el Melloi, en un taller desbocado, desata una cadena de investigaciones por parte de Legislación que puede acabar haciendo que el joven pierda todo derecho sobre la propiedad, así que pide ayuda a nuestro protagonista para descubrir la verdad.

El misterio del taller se intensifica, pero Lord El-Melloi parece tener una idea de lo que ocurre. La aparición de un Black Dog en la mansión comienza a aclarar las cosas.

Gray acude a Reines para que le hable sobre cómo participó su maestro en la Guerra del Santo Grial, pero esta le impone una condición a cambio de dicha información: ir a comprar con ella. Ambas se verán atrapadas junto a Luviagelita en un misterioso incidente. Cuál es el Why done it?

Nuestro Lord sube a bordo del Rail Zeppelin, donde para su sorpresa, encontrará más caras conocidas de las que habría esperado ver. La subasta de Ojos Místicos atrae a todas las grandes casas e incluso a la propia iglesia, pero ¿quién le envió a él la invitación y por qué?

El asesinato de Trisha desencadena una investigación en el Rail Zeppelin, aunque por parte de los propios viajeros, ya que la organización no suele prestar atención a incidentes de ese tipo dado que son relativamente habituales. El misterio para irresoluble y elusivo tanto para pasado como futuro, pero el pasado de nuestro Lord sí está dispuesto a regresar a tormentarlo.

While giving the gravely wounded Lord El-Melloi II an arduous treatment, Gray and the others harbor doubts about an existence of a Servant whose Master is nowhere to be seen. Shishigou and Luvia are continuing their investigation in London where they visit Jean-Mario Supinerra and inquire about a serial murder that took place seven years ago. The respite was momentary as the course of the Rail Zeppelin has been altered, and the train plunges into the Forest of Dead Apostles, the Child of Einnashe. Gray, worried about the weakened Lord El-Melloi, decides to assist Karabo's group that is acting to resume the train's progress. Furthermore, Melvin, who has arrived at the Mystic Eyes Collection Train after hearing of rumors, joins the entourage. Olga Marie, barricading her lonely self after refusing to help Gray, finds a "certain something" in her own room.

Gray and the Servant Hephaestion clash within the Child of Einnashe. However, they are engulfed in an avalanche, inevitably forcing a cease-fire. While they temporarily sheathe their weapons, they speak to each other about their ideologies about the relationship between Masters and Servants. Shishigou and Luvia find out that Trisha was investigating about the serial murders from seven years ago and about the Holy Grail War, and see the link between her and the Rail Zeppelin. As various speculations intertwine, Adashino begins to disclose her own deductions in place of Lord El-Melloi II aboard the Mystic Eyes Collection Train...

As Adashino's deductions are playing out, Lord El-Melloi II makes his comeback. He sees a clue to the identity of the true perpetrator of Trisha's murder from Gray's testimony, and requests Melvin to delay the Mystic Eyes Auction from starting. His objective is to seek assistance from Olga Marie, and grasp conclusive evidence to overturn Adashino's deductions. Meanwhile, in London, Shishigou gathers up Flat and Svin in order to proceed with certain preparations. As each of them reflect upon their own ideas, the fated Mystic Eyes Auction finally begins.

Caules Forvedge is suddenly apprehended as the perpetrator. As Lord El-Melloi II causes the Mystic Eyes Auction to pause while disclosing his deductions, Reines, who is supposedly still in London, rushes over to his side. Thus, Lord El-Melloi II points out the name of the true perpetrator.

Several days after the incident on the Mystic Eyes Collection Train, there was a solemn ritual at Modern Magecraft Theories for Svin's ascendance to the rank of Pride. Lord El-Melloi II looked upon the ritual full of emotion as this ascendance to Pride was while his student was still in his teens. Meanwhile, Gray could not shake off the uneasiness that Lord El-Melloi II would depart for distant lands to participate in the Holy Grail War. While in thought, she bumps into Melvin in the streets bustling with the approach of Christmas.