“The Hall is dark enough,” he muttered.  “Listen!”

They heard the regular pacing of a sentinel in the drive.  Nearer to them, on the top of the wall, they fancied that they heard the clash of a bayonet.  Granet dropped his voice to the barest whisper.

“We are close there now.  Stretch out your hand, Collins.  Can you feel a shelf of rock?”

“It’s just in front of me,” was the stifled answer.

“That’s for the stuff.  Down with it.”

For a few moments Collins was busy.  Then, with a little gasp, he gripped Granet’s arm.  His voice, shaking with nervous repression, was still almost hysterical.

“They’re coming, Granet!  My God, they’re coming!”

Both men turned seaward.  Far away in the clouds, it seemed, they could hear a faint humming, some new sound, something mechanical in its regular beating, yet with clamorous throatiness of some human force cleaving its way through the resistless air.  With every second it grew louder.  The men stood clutching one another.

“Have you got the fuse ready?  They must hear it in a moment.”  Granet muttered.

Collins assented silently.  The reverberations became louder and louder.  Soon the air was full of echoes.  From far away inland dogs were barking, from a farm somewhere the other side of the road they heard the shout of a single voice.

“Now,” Granet whispered.

Collins leaned forward.  The fuse in his hand touched the dark substance which he had spread out upon the rock.  In a moment a strange, unearthly, green light seemed to roll back the darkness.  The house, the workshop, the trees, the slowly flowing sea, their own ghastly faces—­everything stood revealed in a blaze of hideous, awful light.  For a moment they forgot themselves, they forgot the miracle they had brought to pass.  Their eyes were rivetted skyward.  High above them, something blacker than the heavens themselves, stupendous, huge, seemed suddenly to assume to itself shape.  The roar of machinery was clearly audible.  From the house came the mingled shouting of many voices.  Something dropped into the sea a hundred yards away with a screech and a hiss, and a geyser-like fountain leapt so high that the spray reached them.  Then there was a sharper sound as a rifle bullet whistled by.

“My God!” Granet exclaimed.  “It’s time we were out of this, Collins!”

He seized his scull.  Even at that moment there was a terrific explosion.  A stream of lurid fire seemed to leap from the corner of the house, the wall split and fell outwards.  And then there came another sound, hideous, sickly, a sound Granet had heard before, the sound of a rifle bullet cutting its way through flesh, followed by an inhuman cry.  For a moment Collins’ arms whirled around him.  Then, with no other sound save that one cry, he fell forward and disappeared.  For a single second Granet leaned over the side of the boat as though to dive after him.  Then came another roar.