“Let’s turn in and get a good night’s rest.”

“Oh, bother!” retorted the junior engineer.  “I couldn’t sleep.  Tom, I shan’t sleep a wink to-night, for dreading that you’ll turn rascal-helper.  Tell me that you’ve been joking with me, Tom!”

“But I can’t truthfully tell you that,” Reade insisted.  “I am not joking, and haven’t been joking to-night.”

“Then I wish you’d open up and tell me a few things.”

“Wait,” begged Tom.  “Wait until I’m sure that the few things will bear telling.”

With that much Harry Hazelton found that he would have to be content.  He allowed himself to be persuaded to turn in.

Tom Reade was asleep in a few minutes.  It was after two in the morning ere Harry, after racking his brains in vain, fell asleep.

The next morning it was found that the stranger in the back of the cook tent had made good his prophecy by vanishing.

CHAPTER XIX

THE HIDALGO PLANS GRATITUDE

Soon after an early breakfast Tom and Harry were afield.

From behind a window in the upper part of his big house, Don Luis, equipped with a powerful field glass, watched them keenly whenever they were in sight.

“What on earth are the Gringos doing?” he wondered, repeatedly.  “Are they just walking about, aimlessly?  At times it looks like it.  At other times it doesn’t.”

Then Montez sent for Tisco and discussed with him the seeming mystery of the actions of the young engineers.

“Don’t ask me, Don Luis,” begged the secretary.  “I am not clever at guessing riddles.  More, I have not pretended to understand this Gringo pair.”

“Are they, in the end, going to trick me, Carlos?”

“Who can say?” demanded Dr. Tisco, with a shrug of his shoulders.  “Of course, they both know that it will be but a short cut to suicide if they attempt to fool you.”

“Their deaths will cause me no anxiety, Carlos, either before or after the sale,” murmured Montez.  “In fact, my good Carlos—­”

“Say it,” leered Dr. Tisco, as his employer paused.

“I may as well say it, for you have guessed it, Carlos.  Yes, I will say it.  Even if this Gringo pair appear honestly to aid me in making the sale—­and even if I do make the sale and receive the money—­this Gringo pair must die.  We know how to arrange that, eh, my staunch Carlos?”

Dr. Tisco shrugged his shoulders.

“Of course, we can put them out of the way, at any time, with secrecy and dispatch, Don Luis.  But what will be the use—­provided they help you to get the American money into your hands?  To be sure, the new buyers will soon find that they have a worthless mine on their hands, but that may happen with the finest mine.  The new buyers will never be able to prove that you brought all of your pretty-looking ore from another mine.  You can depend upon the secrecy of the people from whom you have been buying the baiting ore for El Sombrero.”