, and from it he brought forth a
circlet of gold set with a large gem--it was the mate to that which I
had taken from Sator Throg.

"He was a Holy Thern," said Xodar. "Fortunate indeed it is for us that
he did not escape."

The officer of the guard entered the chamber at this juncture.

"My Prince," he said, "I have to report that this fellow's companion
escaped us. I think that it was with the connivance of one or more of
the men at the gate. I have ordered them all under arrest."

Xodar handed him the thoat oil and cloth.

"With this you may discover the spy among you," he said.

I at once ordered a secret search within the city, for every Martian
noble maintains a secret service of his own.

A half-hour later the officer of the guard came again to report. This
time it was to confirm our worst fears--half the guards at the gate
that night had been therns disguised as red men.

"Come!" I cried. "We must lose no time. On to Hastor at once. Should
the therns attempt to check us at the southern verge of the ice cap it
may result in the wrecking of all our plans and the total destruction
of the expedition."

Ten minutes later we were speeding through the night toward Hastor,
prepared to strike the first blow for the preservation of Dejah Thoris.

CHAPTER XX

THE AIR BATTLE

Two hours after leaving my palace at Helium, or about midnight, Kantos
Kan, Xodar, and I arrived at Hastor. Carthoris, Tars Tarkas, and Hor
Vastus had gone directly to Thark upon another cruiser.

The transports were to get under way immediately and move slowly south.
The fleet of battleships would overtake them on the morning of the
second day.

At Hastor we found all in readiness, and so perfectly had Kantos Kan
planned every detail of the campaign that within ten minutes of our
arrival the first of the fleet had soared aloft from its dock, and
thereafter, at the rate of one a second, the great ships floated
gracefully out into the night to form a long, thin line which stretched
for miles toward the south.

It was not until after we had entered the cabin of Kantos Kan that I
thought to ask the date, for up to now I was not positive how long I
had lain in the pits of Zat Arrras. When Kantos Kan told me, I realized
with a pang of dismay that I had misreckoned the time while I lay in
the utter darkness of my cell. Three hundred and sixty-five days had
passed--it was too late to save Dejah Thoris.

The expedition was