“I mean that in the last resort, before it returns to the womb of potential fire, it will probably assume the face and figure of its Director, of the man of magical knowledge who originally bound it with his incantations and sent it forth upon its mission of centuries.”

The soldier sat down and gasped openly in his face, breathing hard; but it was a very subdued voice that framed the question.

“And how do you propose to make it visible? How capture and confine it? What d’ye mean, Dr. John Silence?”

“By furnishing it with the materials for a form. By the process of materialisation simply. Once limited by dimensions, it will become slow, heavy, visible. We can then dissipate it. Invisible fire, you see, is dangerous and incalculable; locked up in a form we can perhaps manage it. We must betray it⁠—to its death.”

“And this material?” we asked in the same breath, although I think I had already guessed.