"My dear fellow, you have answered your own question. Because the thing is impossible, it is so easy. I don't mind admitting that I have tried a few experiments myself, but hitherto without success. Still, it won't be so very long before the whole world is lighted with a fluid which will supply burners without wires. Sounds fascinating, doesn't it? At any rate, it fascinated me to the exclusion of everything else. I tried to puzzle it out in the same way that Marconi puzzled out his invention. In my mind's eye, I could see a big fire station, say where my glass is, and a big factory where yours stands. By the use of powerful induction coils it seemed to me that I could force the power into the factory lamps without the aid of wires. Isn't that the way they propose to work telephones?"
"I don't know anything about it," Swift said sullenly.
"Oh, yes, you do," Bark said, with sudden impatience. "You know all about it. And, what's more, a successful attempt has been made within a mile or so of this very spot. More than once, when I was trying my experiments, it occurred to me to come to England to discuss the matter with Arnold Rent. I didn't do so for reasons which I will not go into now. But when business compelled me to come to this country and see Rent, I wasn't surprised to find that he was working on precisely the same thing. But you know that just as well as I do. What is the good of pretending you don't?"
"It pleases you to say so," Swift murmured.
"Yes, and it will please me to prove it before long, if you take that line. Mind you, I should not have known it if it hadn't been for a mere accident. Perhaps you will deny that there is any connection between what we are talking about and the mysterious death of my sister, to say nothing of Mrs. Charlock?"
A sudden exclamation broke from Swift. He seemed to be startled and alarmed. From his hiding-place Grey could almost imagine the satisfied grin on Bark's face.
"Take your time," the latter said playfully. "I won't hurry you, for we sha'n't part till I get to the bottom of this business. I asked you a plain question and I mean to have a plain answer. Have you or has Arnold Rent made any startling discovery in the direction of intermittent electricity? Is the thing within the range of practical politics?"
It was a long time before Swift replied. Grey could hear him playing with his glass. He could hear the uneasy shuffle of the unfortunate man's body. When the electrician did speak his voice was both timid and hesitating.
"You have no business to ask me this," he said. "If we have made the discovery you speak of, it lies entirely between Arnold Rent and myself. A discovery like that means a huge fortune to the author. The richest man in the world would be a pauper alongside the man who could reduce such a discovery to practical uses."
"What a chap it is to talk!" Bark said impatiently. "Why don't you come to the point? You know perfectly well that you dare not refuse the information I am after."