Reinhard von Müsel and Siegfried Kircheis revisit the location of Karl von Reifeisen's death to look for new clues. A falling bag of flour which almost crushed Reinhard gives him a brainwave and he quickly asks Kircheis to confirm something for him. Soon after that, he and Kircheis report their findings thus far to Geahard von Steger, the principal of their alma mater, and insinuate to him that the murderer is Moritz von Haase and even summoned the latter to prove his colour-blindness. However, this is just a ruse to make Steger reveal that he is the actual perpetrator. Reinhard then proceeds to reconstruct the chain of events in their presence and states that while Reifeisen's death was purely an accident, Steger, in an attempt to absolve his responsibility of negligence and to improve the position of his grandson, who is currently ranked third in his cohort, cleared the evidence of the accident to make Reifeisen's death to appear as a murder. He then murdered the second-ranking Johann Gottholp von Bertz in a way that would implicate the first-ranking Haase, whose condition he was aware of. This way, Reifeisen's death would be attributed to Haase as well. With the truth revealed, Steger makes a brief protest before being led away together with Haase by waiting military policemen and the case closes.
Prequel to the original series, focusing on Reinhard and his steps up the chain of command in the Galactic Empire. Also focusing on the FPA's Yang Wen-li. A chronicle on how he earned the title "The Hero of El Facile" and his handling of assignments he received after the historic event. Spiral Labyrinth also continues with the background of Reinhard and Kircheis where the first Gaiden left off.
