Then John’s heart stands still with a sudden fear, as he imagines that some terrible thing has occurred.  He raises his voice and calls upon Philander.  When there comes no reply to this, he makes use of Sir Lionel’s name and bellows it forth until the valley seems to ring with the sound.  Still hopeless, for no answer bids him drop his fears.

Now the fact is assured that something serious has happened.

John jumps to the ground, desirous of seeing whether they have actually reached the spot where the wrecked omnibus lies.

He finds it to be true, and in another moment is standing upon the very place where Aunt Gwen reclined at the time of his departure.

There is much room for speculation.  Any one of half a dozen things might have happened, for to one who is utterly in the dark, there is no end of possibilities.

What can he do?

One chance there is, that while he, Doctor Chicago, was absent, bent upon his errand of mercy and rescue, Mustapha may have once more appeared upon the scene, and influenced the little party to move on in the direction of the distant city.

He still places implicit confidence in the guide, and has strong hopes, though the absence of the Arab at the time of the accident is utterly unexplainable.

By this time monsieur has descended from his perch, and joins him.  In his hand he carries the lantern, ready for use.

“What have you found, mon ami?” asks this worthy, as he arrives on the scene.

“Here is the wrecked stage, but my friends have vanished.  It puzzles me to know what has become of them.”

“No doubt they have gone ahead, fearing that you could not ze new vehicle obtain.  We may soon discover ze truth.”

“By going forward, yes; but before we do that, perhaps I can learn something about the direction they took.”

“Ah! you will apply ze wonderful science of ze prairie.  I have heard of it, begar, and I shall be one very glad to see ze experiment.”

He poses in an attitude of expectation, and keeps his eyes fastened upon the other, who has already picked up the lantern and bends over, with the intention of following the trail.

This soon brings him from the ruined stage to the olive tree under which they had laid Aunt Gwen.

Arrived here he utters an exclamation.

“This tells the story.  Confusion, indeed.”

“What now, monsieur?” echoes the Frenchman.

“See; the tracks are numerous.”

“But they would have been had these people moved about a good deal.”

“Look again.  You will note that they are made by other feet.  Many men have been here.  What you once suggested—­”

“Mon Dieu! robbers?” as if appalled.

“That explanation is nearer the mark that anything else.”

The prospect is appalling, for these wild robbers of the desert fear neither man nor devil, and when once they retreat to their hiding-places in the mountains, it is next to folly to dream of following them.