f for having seemed to give way for a single moment to
softer thoughts than those of conquest and adventure.

Gradually the cradling swing, the quivering power of the airship,
lulled his fevered spirit. Sleep won upon him, dulled the excitements
of the past twenty-four hours, sank him into oblivion. His deep,
regular breathing sounded in the gloom of the cabin that contained
the Great Pearl Star, the Myzab, the sacred Black Stone of infinite
veneration.

An hour he slept. On, on roared _Nissr_, swaying, rising, falling
a little as she hurled herself through the Arabian night toward
the unknown Bara Jannati Shahr, hidden behind the Iron Mountains of
mystery as yet unseen by any unbelieving eye.

Peace, all seemed peace, for one dark hour.

But as the hour ended, a shadow fell along the narrow gallery outside
the cabin window. A silent shadow it was, that crept, paused, came on
again. And now in the dark, had there been any eye to see, the shadow
would have been identified as a barefoot man, lithe, alert, moving
silently forward with the soundless stealth of an Arab versed in the
art of _asar_, or man-stalking.

To the Master's window this shadow crept, a half-invisible thing in
the gloom. It paused there, listening to the deep, regular breathing
within. Then a lean, brown hand was laid on the sill. It still seemed
to hesitate.

Something gleamed vaguely in that hand--a crooked _jambiyeh_,
needle-sharp at the point, keen-edged and balanced for the stroke that
silently slays.

Motionless, unbreathing even, the shadow waited a long minute. Then
all at once over the sill it writhed, quick, lithe as a starved
panther.

Dagger in hand, the shadow slid to the berth where lay the Master of
the Legionaries. There Rrisa paused, listening to the slow respiration
of the White Sheik with whom he had shared the inviolable salt, to
whom he owed life itself.

Up, in the gloom, came the dagger-blade.

Over the unconscious Master it poised, keen, cold, avenging in the
dark of the cabin where lay the three supreme treasures of all Islam.

CHAPTER XXXV

INTO THE VALLEY OF MYSTERY

The upraised blade, poised for swift murder, did not descend. With a
groan from the heart's core, Rrisa let fall his trembling hand, as
he recoiled toward the vague patch of starlight that marked the cabin
window.

"_Bismillah_!" he whispered hoarsely. "I cannot! This is my
sheik--'and thrice cursed is the hand that slays the sheik.' I