been in the house at the time. Unfortunately I had just ridden off, accompanied by Doctor Trenchard here, and Nick Froude, the Harborer of the Staghounds, in an attempt to track the so-called Terror by means of the dogs."
"But," objected the detective, "you all left the house by the back entrance."
"No, by the front." It was Hugh who made the correction. "I distinctly remember taking my hat from the hallstand, and I am certain that the only thing on it at the time was the hat belonging to my friend, Doctor Brewster."
"That's correct," confirmed Ronnie. "There certainly was no letter there when we quitted the house."
"Thank you, gentlemen. Your testimony on that point has been most helpful." Renshaw paused and stroked his chin thoughtfully, his brows drawn down so that they half veiled his keen eyes. "What you have told me has relieved my mind considerably; though I'll admit that, on the face of it, it doesn't seem to give one the slightest hint how the thing was managed. It seems rather to confirm Jopling's secret panel theory, eh? Well, good-night, gentlemen, and once more let me advise you to be careful. Remember that you are for the time being the guardians of a secret that would give an ambitious power the domination of the world, and two human lives would be but a grain of dust in the balance to any one who desired to possess it."
ON this not very reassuring note Inspector Renshaw took his departure. Hugh Trenchard bolted the door behind him, and on re-entering the library stood motionless for nearly a minute, thinking deeply. The inspector's parting words had brought home to him the extremely perilous nature of the secret entrusted to him by Silas Marie. When at last he glanced up, it was to catch Ronnie's eyes fixed on him with an expression of sardonic amusement.
"Getting scared?'
To the questioner's surprize Hugh nodded.
"Frankly, old chap—yes. I am scared of what might happen if the wrong people got hold of that sealed envelope. When I came out here to spend the night I little thought that I should have in my keeping a secret that has already cost the lives of two men"
"One-and-a-half, to be exact,' Ronnie corrected flippantly, "for the village idiot was only half annihilated, according to Marie's account. Not that it seems worth while going into fractions and decimals in a case like that. Anyway, what are you worrying about? Put the envelope in the safe and forget all about it till the morning."
"That safe makes me smile," Hugh declared, shaking his head. "Didn't you notice the rough way in which it has been put together? It appears to have been constructed by an amateur boiler-maker, and a live crook could simply rip it open like cutting through a sardine tin."
“He wouldn't be a 'live' crook very long after he’d started his job," Ronnie declared so confidently that his friend stared at him in amazement.
"Why not?"
"Come with me, and I'll show you."
He led the way from the room, and, crossing the dark passage with an unerring sense of direction, found and turned the handle of the door leading to the laboratory. Inside was a mere cave of velvety blackness, marked at the farther end by an oblong of slightly lighter indigo which showed the position of the single window, Ronnie struck a match and lit
