I had reached the base of the Temple of the Sun!

Somewhere above me lay Dejah Thoris, and with her were Phaidor,
daughter of Matai Shang, and Thuvia of Ptarth. But how to reach
them, now that I had found the only vulnerable spot in their mighty
prison, was still a baffling riddle.

Slowly I circled the great shaft, looking for a means of ingress.
Part way around I found a tiny radium flash torch, and as I examined
it in mild curiosity as to its presence there in this almost
inaccessible and unknown spot, I came suddenly upon the insignia
of the house of Thurid jewel-inset in its metal case.

I am upon the right trail, I thought, as I slipped the bauble into
the pocket-pouch which hung from my harness. Then I continued
my search for the entrance, which I knew must be somewhere about;
nor had I long to search, for almost immediately thereafter I came
upon a small door so cunningly inlaid in the shaft's base that it
might have passed unnoticed by a less keen or careful observer.

There was the door that would lead me within the prison, but where
was the means to open it? No button or lock were visible. Again
and again I went carefully over every square inch of its surface,
but the most that I could find was a tiny pinhole a little above
and to the right of the door's center--a pinhole that seemed only
an accident of manufacture or an imperfection of material.

Into this minute aperture I attempted to peer, but whether it was
but a fraction of an inch deep or passed completely through the door
I could not tell--at least no light showed beyond it. I put my ear