Laura hesitated, puzzled.  Just then the Professor came cantering in with a bundle of grass in his hand.  He glanced down at the Chinaman.

“Good morning, Miss Laura!” he said.  “You don’t seem to be getting on with our friend here,” he added in an undertone.  “If you would permit me to offer you just a word of advice, it really doesn’t pay to annoy these Chinese too much.  They never forget.  I didn’t like the way that fellow was looking at you.  I was watching him all the way from the rise there.”

“Pshaw!” she answered.  “Who cares what a Chink thinks!  The fellow’s an idiot.  I’m worried, Professor.  Lenora’s gone out after Mr. Quest and the Inspector.  She wasn’t fit to ride a horse.  I can’t make out why she’s attempted it.”

The Professor unslung some field-glasses from his shoulder and gazed steadily southward.

“It is just possible,” he said softly, “that she may have received a warning of that.”

He pointed with his forefinger, and Laura peered forward.  Something which seemed to be just a faint cloud hung over the horizon.  The Professor handed her his glasses.

“Why, it’s a fire!” she cried.

The Professor nodded.

“Just a prairie fire,” he replied,—­“very dangerous, though, these dry seasons.  The flames move so quickly that if you happen to be in a certain position you might easily get cut off.”

Laura turned her horse round.

“Come on, Professor!” she exclaimed.  “That’s what it is.  Lenora’s gone to try and warn the others.”

“She is a very brave young lady,” the Professor declared, as he touched his pony with the spurs.  “All the same, Miss Laura, you take my advice and leave that Chinaman alone.”

They rode to the very edge of the tract of country which was temporarily enveloped with smoke and flame.  Here they pulled in their horses, and the Professor looked thoughtfully through his field-glasses.

“The road straight on is the ordinary way to the depot,” he said, “but, as you can see, at the bend there it is becoming almost impassable.  The thing is, what did Lenora do?  When she got as far as this, she must have seen that further progress was dangerous.”

Laura gave a little cry and pointed with her riding-whip.  About twenty yards further on, by the side of the road, was a small white object.  She cantered on, swung herself from her horse and picked it up.

“Lenora’s handkerchief!” she cried.

The Professor waved his arm westward.

“Here come Quest and the Inspector.  They are making a circuit to avoid the fire.  The cowboy with them must have shown them the way.  We’d better hurry up and find out if they’ve seen anything of Miss Lenora.”

They galloped across the rough country towards the little party, who were now clearly in sight.

“Lenora isn’t with them,” Laura declared anxiously, “and look—­what’s that?”