Jimgrim by Talbot Mundy

There was no smell or sign of gas in the rock-hewn chamber where we had fought with Bertolini's gang, but there were five men lying on the floor who had died so instantaneously that their nerves had not had time to make their muscles move and register pain or even a spasmodic struggle. There was a careful autopsy performed on them, and on the dead men in the other cavern, late that evening and not a trace of anything was found that could explain why or how they had died. They were dead; the life was separated from their bodies; that was all that even chemical analysis could answer.

Nor was there the slightest trace of gas or of any detectible rare element within the tunnel leading downward from the cavern, although later in the day men came and chipped small pieces from the stone and those were crushed and chemically tested. Nobody believed our tale about the gas until a too incredulous laboratory expert opened one of the glass flasks taken from the drawer in the Chinese butler's room. That expert and his five assistants died so swiftly that the only good they did was to suggest how other unexplained deaths, in many countries, might have happened. There are nine of those flasks remaining for some genius to open, if he dares, and analyse if he can find a way to do it. And there may be others; nobody knows how many gallons of that deadly liquid Dorje sent to different quarters of the globe for the removal of objectionable people. All we do know is that Dorje's factory is now as lost forever as the secret of the means by which men built the Pyramid, of blocks that weigh eight hundred tons apiece, before even wheels were in regular use or steam and electricity were known. We know no more, comparatively, than the ancients did; their ignorance of what we know was probably not greater than our ignorance of principles they understood. And when a man like Dorje taps a new vein of the infinite resources of the universe, he leaves our ablest scientists as ignorant as cavemen gaping at a radio receiving set.