It was flushed with gray. A faint mist of silver-gray was born in it, and filled it, and became brighter, until it was a cube of silver flame.

A bell note pealed from the instrument, clear, deeply golden. Its liquid reverberations trembled and shattered into silence. And the silver light ran out of the cube like molten metal.

It left the figure of a man. The cube was invisible ; the figure seemed to stand before us, on a little argent table. It was only two feet high; only, I knew, an image. But no reality could have been more vividly real.

It was an old man, robed strangely and in white, with the grave stamp of an austere power upon his solemn face.

He gestured for attention, with a manner of serene authority. His lips moved. He spoke. His voice rang clear in the darkened chamber — though I knew it came across forty million miles of space and forty thousand years of time.

Don touched another lever. The voice stopped. The molten silver rose again, filled the cube, faded to blackness. The humming ceased. Don — to my relief — snapped on the lights.

“You see, now, Red, how I know.”

“You could — understand?”