A scuff mark on the floor was evidence in Ryunosuke Naruhodo's investigation into what had happened to Kazuma Asogi on board the SS Burya.
Shoe polish[]
- Main article: The Adventure of the Unbreakable Speckled Band
On January 9, a little past midnight, Nikolina Pavlova visited Asogi's cabin, which was next door to her own, to retrieve her cat Darka. Asogi helped Pavlova find her cat, but also recognized her, causing her to admit that she had run away from her ballet troupe, Novavich Ballet. Pavolva grew fearful that Asogi would call on someone else and expose her secret, and pushed him in a panic. This caused Asogi to step on a bell worn by Darka, breaking it in two, leaving a dark stain, and slip. He fell to the floor and was knocked unconscious.
Bif Strogenov heard the noise and headed to the cabin, where Pavlova explained what had happened. Finding the sleeping Naruhodo inside Asogi's wardrobe, Strogenov decided to alter the scene to frame the stowaway. Among the measures that he took was to find half of a bell worn by Darka, and dispose of it in the wastepaper basket in Pavlova's cabin, failing to find the other half in the darkness. He then triggered the ship's emergency stop, using the deceleration to slide the bolt shut on Asogi's cabin, thereby creating a locked-room scenario pointing to Naruhodo as the only person who could have possibly attacked Asogi.
Asogi was found lifeless the next morning, and Herlock Sholmes investigated what he called "this curious murder". He found the mark on the floor and used his chemical analysis tools to determine that it was shoe polish. Naruhodo later found out about this and identified it as coming from Asogi's shoes. This eventually led to the conclusion that Asogi had broken his neck after slipping on Darka's bell. Pavlova tried to "admit" that this had all been an accident, but the halves of the bell being in separate cabins helped to reveal the true story.