nch 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
to it next and listened, but again my efforts brought negligible
results.

During these experiments Woola had been standing at my side gazing
intently at the door, and as my glance fell upon him it occurred
to me to test the correctness of my hypothesis, that this portal
had been the means of ingress to the temple used by Thurid, the
black dator, and Matai Shang, Father of Therns.

Turning away abruptly, I called to him to follow me. For a moment
he hesitated, and then leaped after me, whining and tugging at my
harness to draw me back. I walked on, however, some distance from
the door before I let him have his way, that I might see precisely
what he would do. Then I permitted him to lead me wherever he
would.

Straight back to that baffling portal he dragged me, again taking
up his position facing the blank stone, gazing straight at its
shining surface. For an hour I worked to solve the mystery of the
combination that would open the way before me.

Carefully I recalled every circumstance of my pursuit of Thurid,
and my conclusion was identical with my original belief--that Thurid
had come this way without other assistance than his own knowledge
and passed through the door that barred my progress, unaided from
within. But how had he accomplished it?

I recalled the incident of the Chamber of Mystery in the Golden
Cliffs that time I had freed Thuvia of Ptarth from the dungeon of
the therns, and she had taken a slender, needle-like key from the
keyring of her dead jailer to open the door leading back into the
Chamber of Mystery where Tars Tarkas fought for his life with the
great banths. Such a tiny keyhole as now defied me had opened the
way to the intricate lock in that other door.

Hastily I dumped the contents of my pocket-pouch upon the ground
before me. Could I but find a slender bit of steel I might yet
fashion a key that would give me ingress to the temple prison.

As I examined the heterogeneous collection of odds and ends that
is always to be found in the pocket-pouch of a Martian warrior