single file.

Alice's eyes strayed from the backs of her two companions to the
mountains that rolled upward from the little valley, their massive
peaks and buttresses converted by the wizardry of moonlight into a
fairyland of wondrous grandeur. The cool night air was fragrant with
the breath of growing things, and the feel of her horse beneath her
caused the red blood to surge through her veins.

"Oh, it's grand!" she whispered, "the mountains, and the moonlight, and
the spring. I love it all--and yet--" She frowned at the jarring note
that crept in, to mar the fulness of her joy. "It's the most wonderful
adventure I ever had--and romantic. And it's _real_, and I ought to be
enjoying it more than I ever enjoyed anything in all my life. But, I'm
not, and it's all because--I don't see why he had to go and drink!"
The soft sound of the horses' feet in the mud changed to a series of
sharp clicks as their iron shoes encountered the bare rocks of the
floor of the canyon whose precipitous rock walls towered far above,
shutting off the flood of moonlight and plunging the trail into
darkness. The figures of the two men were hardly discernible, and the
girl started nervously as her horse splashed into the water of the
creek that foamed noisily over the canyon floor. She shivered slightly
in the wind that sucked chill through the winding passage, although
back there in the moonlight the night had been still. Gradually the
canyon widened. Its walls grew lower and slanted from the
perpendicular. Moonlight illumined the wider bends and flashed in
silver scintillations from the broken waters of the creek. The click
of the horses' feet again gave place to the softer trampling of mud,
and the valley once more spread before them, broader now, and flanked
by an endless succession of foothills.