“Evocation?” whispered Henriot, more distressed than he cared to admit.

Vance nodded.  Leaning still closer, to his companion’s face, he thrust his lips forward, speaking eagerly, earnestly, yet somehow at the same time, horribly:  “And we want—­my aunt would ask—­your draughtsman’s skill, or at any rate your memory afterwards, to establish the outline of anything that comes.”

He waited for the answer, still keeping his face uncomfortably close.

Henriot drew back a little.  But his mind was fully made up now.  He had known from the beginning that he would consent, for the desire in him was stronger than all the caution in the world.  The Past inexorably drew him into the circle of these other lives, and the little human dread Vance woke in him seemed just then insignificant by comparison.  It was merely of To-day.

“You two,” he said, trying to bring judgment into it, “engaged in evocation, will be in a state of clairvoyant vision.  Granted.  But shall I, as an outsider, observing with unexcited mind, see anything, know anything, be aware of anything at all, let alone the drawing of it?”

“Unless,” the reply came instantly with decision, “the descent of Power is strong enough to take actual material shape, the experiment is a failure.  Anybody can induce subjective vision.  Such fantasies have no value though.  They are born of an overwrought imagination.”  And then he added quickly, as though to clinch the matter before caution and hesitation could take effect:  “You must watch from the heights above.  We shall be in the valley—­the Wadi Hof is the place.  You must not be too close—­”

“Why not too close?” asked Henriot, springing forward like a flash before he could prevent the sudden impulse.

With a quickness equal to his own, Vance answered.  There was no faintest sign that he was surprised.  His self-control was perfect.  Only the glare passed darkly through his eyes and went back again into the sombre soul that bore it.

“For your own safety,” he answered low.  “The Power, the type of life, she would waken is stupendous.  And if roused enough to be attracted by the patterned symbol into which she would decoy it down, it will take actual, physical expression.  But how?  Where is the Body of Worshippers through whom it can manifest?  There is none.  It will, therefore, press inanimate matter into the service.  The terrific impulse to form itself a means of expression will force all loose matter at hand towards it—­sand, stones, all it can compel to yield—­everything must rush into the sphere of action in which it operates.  Alone, we at the centre, and you, upon the outer fringe, will be safe.  Only—­you must not come too close.”

But Henriot was no longer listening.  His soul had turned to ice.  For here, in this unguarded moment, the cloven hoof had plainly shown itself.  In that suggestion of a particular kind of danger Vance had lifted a corner of the curtain behind which crouched his horrible intention.  Vance desired a witness of the extraordinary experiment, but he desired this witness, not merely for the purpose of sketching possible shapes that might present themselves to excited vision.  He desired a witness for another reason too.  Why had Vance put that idea into his mind, this idea of so peculiar danger?  It might well have lost him the very assistance he seemed so anxious to obtain.