The interior of the greenhouse was bare of pots and plants; for four-fifths of its length it was bare of anything at all. There was a rough concrete floor, and the concrete extended up the sides of the greenhouse for about three feet, thus forming a kind of trough. And at one end of the trough there was tethered a goat.
At the other end of the building, on a kind of staging set on short concrete pillars, stood four men.
The Saint took them in at a glance. Three of them stood in a little group—a fat little man with a bald head and horn-rimmed spectacles, a tall, thin man of about forty-five with a high, narrow forehead and iron-grey hair, and a youngish man with pince-nez and a notebook. The fourth man stood a little apart from them, in front of a complicated switchboard, on which glowed here and there little bulbs like the valves used in wireless telegraphy. He was of middle height, and his age might have been anything from sixty to eighty. His hair was snow-white, and his clothes were shapeless and stained and shabby.
But it was on nothing human or animal in the place that the Saint's gaze concentrated after that first swift survey.
There was something else there, on the concrete floor, between the four men and the goat at the other end. It curled and wreathed sluggishly, lying low on the ground and not rising at all; and yet, though the outside of it was fleecily inert, it seemed as if the interior of the thing whirled and throbbed as with the struggling of a tremendous force pent up in ineffectual turmoil. This thing was like a cloud; but it was like no cloud that ever rode the sky. It was a cloud such as no sane and shining sky had ever seen, a pale violet cloud, a cloud out of hell. And here and there, in the misty violet of its colour, it seemed as if strange little sparks and streaks of fire shot through it like tiny comets, gleamed momentarily, and were gone, so that the cloud moved and burned as with an inner phosphorescence.