“By gum!” he muttered, gazing at its spacious depths, “I never thought of that.”

“You see what I’m driving at, then?”

“Why, of course, sir.  A moderate-sized man could stow away inside there and hoist himself to any floor.  It ‘ud be perfectly easy an’ safe as nails.  A hundredweight of coal is nothing to it.”

“I think we see now at least one method whereby the man who killed Mrs. Lester could have entered the flat without her knowledge?”

“Not a doubt about it, sir.  Nearly noiseless, too, an’ if you heard it working you’d imagine it was meant for the flat beneath, because there’s a whistle to warn us when it’s comin’ here.”

They surveyed the lift in silence for a little while.  Then Bates caused it to descend again, and Theydon examined the rather flimsy device which fastened the panel.

“I’m not what you might describe as a nervous individual,” he said, at last, “but it wouldn’t be fair to your wife and yourself, Bates, if I didn’t tell you I have just received an ugly reminder that the gang which killed Mrs. Lester has a grudge against me now.  Wouldn’t it be a reasonable thing if we drove a couple of screws into that door tonight?”

Bates stroked his chin.  The long-dormant spirit of combat kindled in his eye.

“Better still, sir,” he grinned, “let’s drive a screw into any one who comes up in the lift.”

“But how?”

“By tying your pistol firmly to the dresser, putting it on a hair-trigger—­ I know how to do that, of course—­ an’ letting it plug a bullet into the right place when the panel is half open.”

“Are we justified in taking the law into our own hands?”

“Is any one justified in tryin’ to get in here an’ cut our throats while we’re asleep, sir?”

Theydon weighed the pros and cons of this thesis very carefully.  He dreaded the possibility of taking a human life, even in self-defense.  Yet against the wretches who had strangled Edith Lester, and coolly prepared to leave Mrs. Forbes to starve in an empty house until their revengeful scheme was perfected by full knowledge of the identity of every man in China, who had assisted in the downfall of an effete monarchy, what code of conduct would apply unless it were that which holds sway in the jungle?

“Couldn’t we contrive matters so that if the pistol were fired it need not necessarily inflict a fatal wound?” he said.

“Let’s see what we can do, sir,” and Bates set to work gleefully on the arrangements.  There was not the slightest difficulty in devising an efficient means of pressing a trigger with a reduced pull by opening the door.  Any schoolboy could adjust a piece of string to act unfailingly.  By measuring distances, and careful sighting of the pistol when fixed in position, they arrived at a line of fire which would strike a body crouched in the lift about the region of the right shoulder.

Then Bates locked the scullery door, put the key in his pocket, and assured his trembling wife that she might sleep like a top, since no bloomin’ Chinaman could get at her that night.  Theydon himself retired soon afterwards.  He was as tired as though he had been trudging steadily along country roads since daybreak.