“One should always look for a possible alternative, and provide against it. It is the first rule of criminal investigation.” -- S. Holmes
Holmes repeatedly stabs a pig in order to prove a point about murder.
I would rate this story much higher, but the mystery is far too easily solved, given the clues presented. So, Detective Stanley Hopkins asks for help with the murder of a malicious sailor called Black Peter who was pinned to the wall of his cabin with a harpoon. The first half of the story is Hopkins recounting his work so far and attempting to convince Holmes to help.
The one clue is a notebook that appears to be dropped at the scene of the crime. Believing the burglar/killer did not succeed in entering the crime scene to retrieve it, they presume to catch him the next night while making a second attempt. So they wait in the bushes by the outhouse.
A young man, J. H. Neligan, is tracking down Black Peter in order to gain access to Peter’s logbooks and clear his father’s name when securities that he held came on the market. It appears that this young man is the killer. Hopkins arrests him.
Holmes has many aliases for his disguises in different parts of London, such as Basil.
After much thought, Holmes has Watson write two telegrams. The first invites Hopkins over for breakfast and, the next morning, Holmes proceeds to disprove the outcome of Hopkins' arrest with detailed reasoning.
Mrs. Hudson prepares breakfast for Holmes and Watson.
In answer to the other telegram, three men arrive, each to be hired for a job. Harpooners. Holmes pays the first two and sends them off. The third, he wrestles to the ground and accuses of Black Peter’s murder. This man, Patrick Cairns, admits to killing Black Peter in self-defense. Funny enough, he also forgot something at the outhouse, his tobacco pouch, to be found by Hopkins at the scene, but ignored.
Not a bad story but I also believe that Hopkins isn’t looking at the obvious clues and allows his eagerness for an arrest to carry him off track.