A/N: I felt this case deserved more time. I'm not entirely happy with it. Perhaps one day I'll have time to go back and expand upon it.
Prompt from sirensbane: One of the stories Watson will never publish.
"Somewhere in the vaults of the bank of Cox and Co., at Charing Cross, there is a travel-worn and battered tin despatch-box with my name, John H. Watson, M.D., Late Indian Army, painted upon the lid. It is crammed with papers, nearly all of which are records of cases to illustrate the curious problems which Mr. Sherlock Holmes had at various times to examine."
The Sussex Vampire, ACD
The Case of the Dead Silver Miner
"I've never seen anything like it," the pathologist gestured toward his findings on the corpse of Mr Burrows. Holmes ignored him. Instead, he began an examination of the victim's toenails.
"Poison?" Watson glanced over the pathologist's preliminary report.
"Circumstances point to murder. The needle mark on the man's neck is consistent with an injected poison. There are so many poisons to consider and so far every test I've run have turned up negative. Yet, his death was not accidental." The pathologist shrugged.
Holmes finished abruptly, "poison by injection." He pointed out the skin break on Mr Burrow's neck.
"Um, yes," the pathologist cleared his throat, "I believe we were just discussing such."
"Recently back from the southwest of America and judging by the state of his nails, a prospector for precious metals, most likely silver given his geographical location."
The pathologist's eyes widened as he checked Mr Burrows files, "but how did you know?"
"Don't ask," Watson quickly intercepted Holmes' lecture. "I believe my partner's interest in your case is clear. We'll take it."
As was his custom while engaged on a case, Holmes was hardly seen in the ensuing weeks. It was a snowy evening when Watson came back and found the man hovering over his chemicals; toxic fumes filling their flat.
The doctor set his medical bag down. "Well?" He waited.
"Murder," the detective's eyes narrowed.
"I confess I am wholly in the dark as to how you reached so spectacular a conclusion," Watson settled into his chair.
Like an artist revealing his masterpiece, Holmes outlined the case. "It was simple once I discovered that the victim, Mr Burrows, had recently broken off a partnership with John Quicksilver. They had a disagreement regarding their silver mine wherein Mr Burrows abruptly returned to England and Quicksilver disappeared."
"Your guess about the victim's mining in the southwest of America was correct," Watson recalled.
Holmes stopped and frowned. "How many times must I remind you, Watson, I never guess. My analysis of the victim's origin and profession was based on a careful examination of the victim's skin tones, global weather patterns, and soil analysis from samples under his toenails." He sniffed.
"Yes, of course," Watson apologised. "Please continue," he reached for pen and paper to continue note taking.
With a shake to rearrange his ruffled ego, Holmes resumed. "I shall not bore you with the steps I took, but suffice it that eventually I located John Quicksilver's residence. Several small leather satchels, now empty, were found. Analysis of the dirt residue matched the same as that under the victim's nails. With the help of a contact in America, I confirmed the sacks previously contained silver obtained from Burrow and Quicksilver's mine."
"So, Quicksilver must has double-crossed his partner and stolen all the profits."
"Or, just as likely, Burrows took off with all the silver to England and Quicksilver followed him," Holmes countered. "Curiously, in addition to the leather sacks, I found two reptiles in Quicksilver's room, stout lizards with stumpy legs and tails as wide as their bellies. Their studded reptilian scales were an alarming black and orange."
"Let me guess…" Watson caught himself and help up a hand, "I mean, conclude with confidence based on scientific literature. The lizards were Heloderma suspectum, also known as Gila monsters. A species of venomous lizard native to that region where Burrow and Quicksilver had their mine."
"You are correct, Watson," the detective's voice was unusually baffled. "How did you know?"
Dr George Goodfellow of Tombstone has written several articles on his own scientific research with the species in Scientific America. Most recently he wrote a report on his personal experience with a bite from one of his captive lizards. He was laid up in bed for five days and described the pain as 'molten lava coursing through my veins'
"I fear I shall never get your depths, doctor."
Watson continued," the Gila monster produces a neurotoxin in its salivary glands. One bite, although not fatal, causes excruciating pain, swelling, and weakness in its victim. It is often regarded as the most painful venom of any vertebrate."
Holmes looked admiringly at his friend. "My dear fellow! I am in your debt. You have provided the final puzzle piece. The clue to the poison John Quicksilver used to kill his partner. With his knowledge and access to these reptiles, he must have extracted the perfect poison from these lizards, essentially undetectable by any laboratory."
Watson smiled. "A most remarkable case."
"Yes, Watson, a memorable case and one that I owe you a debt of gratitude for providing the final chapter. Thank you."