A Riddle in Bronze

to run me down.
"Speak, Mr Jones," said Roberta, as she chased a piece of egg around her plate with a fork. "You have a question, I'm sure."
"It's about your father's watch," I said, in a low voice. "Can it really cause a bell to ring at a distance?"
She smiled. "You heard him summon me, then?"
"Yes, just after he received the letter."
Roberta paused, the fork halfway to her mouth. Then she turned to the head of the table. "There was a letter, father?"
The professor lowered his paper. "A missive from Lady Eames. I will deal with her case this afternoon."
"I think not."
"I am perfectly capable of—"
"Father, do you recall the last time you visited a client on your own?"
There was a strained silence, during which they attempted to stare each other down, and then the professor's will broke. Without uttering a word, he busied himself with the newspaper once more.
The battle resolved, I raised the subject of the watch once more.
"What do you know about the properties of metal?" Roberta asked me, in a low voice.
"Precious little, if I'm honest."
She launched into a brief explanation of melting, pouring and casting, and as she spoke I wondered whether this was the reason for her worker's garb, and the soot, and her flushed appearance. However, she was speaking in an animated fashion and I didn't care to interrupt.
Eventually, however, she reached the end of her brief explanation. I guessed she had omitted much of the detail, for her purpose was not to educate me, but to give me a grounding so that she could move on to the next part: how a common pocket watch could make a distant bell ring on command.
"It's my father's greatest discovery. Castings from the same pouring are connected, you see, and this connection can be fortified by the addition of certain elements and other… ingredients."
"Such as?"
"Oh no, Mr Jones," she said, with a laugh. "We do not give our secrets away so lightly."
Professor Twickham grunted from behind his newspaper, this time in agreement.
"Suffice to say," continued Roberta, "we have not yet perfected the process, nor have we discovered all the many combinations of metals and additives that might react in new and interesting ways. So far, we have but a handful of discoveries to our name, but in time they will grow, you can be sure of that."
"But this is immense," I said, as I realised the implications. "Why, the military uses alone…"
The professor came alive of a sudden, bunching the newspaper with one hand in order to slam his fist on the table. "Do not speak of the military in my house," he growled, as the blow rattled plates, cutlery and teacups alike. "Neither those dunderheads, nor the idiot politicians, nor—"
"Calm yourself, father," said Roberta mildly.
"I'm going to my study," said the professor, and he departed the room in a huff, leaving the crumpled newspaper lying across the table.
"I'm sorry, I didn't mean to upset your father," I said, as his footsteps receded down the hall.
"You weren't to know," said Roberta quietly. "He tried to sell the idea once, but a room full of experts laughed him out of the meeting."
"But surely a practical demonstration must have swayed them?"
"They put it down to trickery. Unfortunately, father has a somewhat colourful past." Roberta eyed me, unsure how much to share. "In years past, he convinced investors to fund a number of well-intentioned schemes, but alas they did not come to fruition. People lost their money, and in many circles my father was regarded as a charlatan at best, and a fraud at worst."
"But that's unfair!" I cried. "I've witnessed two unexplained mysteries in this house already, and I've been here less than a single day. These people would only have to see—"
"Please, Mr Jones. I will not have my father exposed to ridicule again. He's accepted his lot, and I'll ask you not to upset him."
She was almost desperate in her pleading with me, and I couldn't very well argue. "I understand," I said, but inside I was excited by the possibilities. The professor and his daughter had discovered a fantastic new property in ordinary, everyday metals, and apparently there were many more discoveries to come. I foresaw endless practical applications for this store of unique knowledge, and my brain conjured up balance books overflowing with pounds, shillings and pence. I had an image of the professor and his daughter wealthy beyond measure, and I confess there was a selfish element too, because such riches in their pockets would surely inspire them to raise my own meagre wages.
But it all seemed for naught, because the professor was unwilling to risk his reputation. I noticed Roberta was still looking at me, unconvinced, and I took her hand in both of mine. "Roberta, I vow to obey your wishes."
She smiled at that, and I saw her relax. Then she got up to retrieve the letter, which she read quickly.
"Your father mentioned a case…" I began delicately. I didn't mean to pry, but they'd told me nothing about the nature of my job, and I was naturally curious.
She looked at me across the top of the letter. "Do you believe in spirits? Ghosts and phantasms and the like?"
I laughed. "I'm a bookkeeper. I believe in neat columns of figures."
"I see."
From the tone of her voice, I realised I'd erred in making light of the question. "In truth, I have an open mind. But why do you ask?"
Slowly, Roberta folded the letter, placing it on the table. "In order to further our discoveries, my father and I need money. And in order to earn money, we perform certain services for wealthy patrons. Services you might find distasteful."
My mind leapt to several conclusions, one of them very distasteful indeed. But no, that simply wasn't possible.
Roberta noticed my expression. "It's nothing illegal or immoral, I assure you." She hesitated. "Some folk, especially the elderly, are beset by… worries. We help to soothe their troubles."
I was completely in the dark, and her skirting around