It was a raw April afternoon in 1889, the rain on the window pane streaked pea-soup yellow from the morning’s fog, and I was sitting in the parlor that I shared with Ponder Wright, the man known throughout London as the Mechanical Detective. He was reading a copy of the Times and I sat across from him, staring idly at my empty glass, half-asleep from the ennui of the weather and a day empty of employment. Abruptly my friend spoke, his voice carrying that odd undertone of metallic echo from the copper plating of his chin and upper larynx.

“The measurements are one point eight grams of sodium bicarbonate, and slightly less, one point six four, of tartaric acid. Both powders are located in the top left drawer of my laboratory desk.” He then turned a page of the paper, sending it and the sleeve of the red silk dressing gown he wore this afternoon fluttering. “And mind you measure them out precisely.”

I stared at him in astonishment. As his friend and mechanic, I believed I had a fair overview of Ponder Wright’s myriad abilities. Yet till now I had not been aware that he could read minds.

“What? Why?”

“Because, my dear Danvers, the gasogene that you purchased last Tuesday, which I deemed a silly frivolity, requires those two chemicals to operate.”

“And how did you know I was thinking of filling and operating the gasogene?” Wright lowered his copy of the Times and looked at me, his blue left eye merry and the lens of his right eye glowing an ember red from within the copper plating of the right side of his face.

“A simple deduction. You were looking at your glass, wondering if it was yet time for either gin or whiskey, either of which would be greatly augmented by a splash of tonic or soda water. Since yesterday afternoon we’ve lacked both, which as I recall was your rationale for purchasing the gasogene in the first place.”

The Cockney salesman who sold me this intriguing contraption (“quite the item among the fashionable Consulting Detective set, I assure you sir”) had not supplied me with an instruction manual, and with little knowledge of chemistry I left the device on the sideboard for future contemplation.

I crossed to it now and unscrewed the top of the two glass globes, then turned to Wright’s laboratory table and removed the appropriate envelopes of powder. “You’ll want to fill the bottom chamber with the powders, and then put water in the upper one,” Wright said, as he took another of his abominable herbal lozenges from the bowl at his side.

“I don’t recall asking for your assistance,” I said, measuring the powders.

“You did not,” he agreed. “But seeing as even the prescribed chemicals in improper amounts have been known to cause gasogenes to explode, my assistance contributes to both your physical health and the safety of our living quarters.”

It was still early enough in our acquaintance for me to find his behavior annoying. Three months prior I had responded to his advertisement for a mechanic surgeon in an attempt to supplement my paltry military pension. I performed maintenance on his prosthetics through the morning, stayed for a tea which turned into a dinner, and we parted late that evening as friends. The next week when I dropped by for a visit he suggested I move in as a flatmate, paying a reduced rent if I agreed to be his on-call mechanic. Since my own lodgings were both dear and geographically disadvantaged, I agreed, and so for the last three months we had enjoyed a relatively pleasant co-habitation of his spacious and centrally located flat on Clacker Street.

Now we lived companionably enough, him pursuing his vocation and me at least dabbling in mine. While I still took on the occasional case, I had seen enough of wounded and dying men with the Royal Steam Artillery, enough blood and rust, to last a lifetime. So I chiefly followed my art by maintaining the delicate machinery of Wright’s prosthetics—both legs, his right arm, and the right hemisphere of his face which included an automatonic ear (a devil to calibrate) and an automatonic eye, supplied with a number of specialized lenses. Though the eye was lidless with an opaque lens, and the brow merely painted on to the brass plate, my friend was capable of a remarkable amount of expression with it. I would swear at times I saw it wink.

As I filled the second globe with water, he shook the paper and gave a snorting laugh. “Another triumph for the Great Detective, I see.” Like many brilliant men Wright had more than a fair share of vanity, and it galled him to see the successes of his rivals.