“ ‘Edith!’ I cried. ‘I think I have it! The grey rock opens five minutes after upon the moonrise. But whoever or whatever it is that comes through it must wait until the moon has risen higher, or else it must come from a distance. The thing to do is not to wait for it, but to surprise it before it passes out the door. We will go into the inner court early. You will take your rifle and pistol and hide yourself where you can command the opening⁠—if the slab does open. The instant it opens I will enter. It’s our best chance, Edith. I think it’s our only one.’

“My wife demurred strongly. She wanted to go with me. But I convinced her that it was better for her to stand guard without, prepared to help me if I were forced again into the open by what lay behind the rock.

“At the half-hour before moonrise we went into the inner court. I took my place at the side of the grey rock. Edith crouched behind a broken pillar twenty feet away; slipped her rifle-barrel over it so that it would cover the opening.