I had come off watch, and Harry and Desiree had taken my place.  Before I lay down I had taken some water to the prisoner, for we had some time before admitted the necessity of giving him drink.  But of food he had had none.

Harry told me afterward that I had slept for two or three hours, but it seemed to me rather as many minutes, when I was awakened by the sound of his voice calling my name.  Glancing at the doorway, I sprang to my feet.

The stone was slowly rising from the floor; already there was a space of a foot or more.  Desiree and Harry stood facing it in silence.

“You have seen nothing?” I asked, joining them.

“Nothing,” said Harry.  “Here, take one of these clubs.  Something’s up.”

“Of course—­the stone,” I observed facetiously, yawning.  “Probably nothing more important than a bundle of quipos.  Lord, I’m sleepy!”

Still the stone moved upward, very slowly.  It reached a height of two feet, yet did not halt.

“This is no quipos” said Harry, “or if it is, they must be going to send us in a whole library.  Six inches would have been enough for that.”

I nodded, keeping my eyes on the ever-widening space at our feet.

“This means business, Hal.  Stand ready with your club.  Desiree, go to the further corner, behind that seat.”

She refused; I insisted; she stamped her foot in anger.

“Do you think I’m a child, to run and hide?” she demanded obstinately.

I wasted no time in argument.

“You will go”, I said sternly, “or I shall carry you and tie you.  This is not play.  We must have room and know that you are safe.”

To my surprise, she made no reply, but quietly obeyed.  Then, struck by a sudden thought, I crossed to where she stood behind a stone seat in the corner.

“Here,” I said in a low tone, taking the little jeweled dagger from my pocket and holding it out to her, “in case—­”

“I understand,” she said simply, and her hand closed over the hilt.

By that time the stone was half-way to the top of the doorway, leaving a space over three feet high, and was still rising.  I stood on one side and Harry on the other, not caring to expose ourselves immediately in front.

Suddenly he left his post and ran to one of the stone seats and began prying at the blocks of granite.  I saw at once his intention and our mistake; we should have long before barricaded the door on the inside.  But it was too late now; I knew from experience the difficulty of loosening those firmly wedged blocks, and I called out: 

“No good, Hal.  We were fools not to have thought of it before, but there is no time for it now.  Come back; I couldn’t stop ’em alone.”

Nevertheless, he continued his exertions, and succeeded in getting one of the blocks partially free; but by that time the doorway was almost completely uncovered, and he saw the folly of attempting further.