They advanced cautiously as far as the bridge, but at that point Brennan turned his pony’s head southward, and spurred the reluctant animal up the steep bank.  Without question Westcott followed, and the two horses broke into a trot as soon as they attained the more level land beyond.  They were slightly above the town now, and could gaze back at the glittering lights in the valley below.  The sound of men’s voices failed to reach them over the soft pounding of the ponies’ hoofs on the prairie sod, but suddenly the distant crackling of a half dozen shots pierced the silence, and their eyes caught the sparkle of the discharges, winking like fireflies in the night.  Before they could draw up their mounts, the fusillade had ended, and all beneath them was unbroken gloom.

“Must be rushing the rock,” commented Westcott.

“More likely saw something and blazed away at it, just as they did at that log,” and Brennan laughed.  “Anyhow they haven’t discovered we have vanished yet.  With an hour more we’ll be where trails are unknown.”

“In the desert?”

“That is the only safe hiding place around here.  Besides we’re carrying a message to Mendez.”

“Without the slightest knowledge of where that party is.”

“Well, hardly that, Jim.  I may not know exactly, but I’ve got a glimmer of a notion about where the cuss hangs out, an’ I’m going to have a hunt for it.  There’s five thousand dollars posted down in Arizona for that fellow, dead or alive; an’ I need the money.  Besides, I reckon this yere Miss Donovan, an’ yer ol’ partner—­what’s his name?—­sure, Cavendish—­will be mighty glad to see us.  You’re game for a try, ain’t yer?”

“I shall never stop until I do find them, Dan,” said the other earnestly, the very tone of his voice carrying conviction.  “Every cent of reward is yours; it will be satisfaction enough for me to know those two are safe.”

“That’s how I figured it.  Now let’s trot on; we ain’t gaining nothing by sittin’ our saddles here.  We can talk while we travel.”

There was a few moments of silence, both men evidently busied with their thoughts; then Westcott asked: 

“What is your idea, Dan?”

The marshal rode steadily, humped up over his saddle-horn, his eyes on the uncertainties in front.

“I ain’t really got none,” he admitted doggedly, “less it be a blind trust in Divine Providence; still I got a medium strong grip on a few things.  That Capley girl told you that Matt Moore drove out on the ridge road?”

“Yes; I asked her about that twice.”

“Well, he likely was headed for this yere Sunken Valley.  That’s point number one.  But he never followed the ridge road very far, for it skirts the desert.  He must have turned off south—­but where?”

“Near the lone cottonwood is my guess.”

“Why?”

“Because there is a swale there of hard sand, which is easily followed, and leaves no trail.  On either side for miles the sand is in drifts, and no two horses would ever pull a wagon through it.  This hard ridge, which is more rock than sand, goes straight south to Badger Springs, the only place to get water.  I was there once, three years ago.”