“But what on earth—­”

“Harry, old fellow, Don Luis is the essence of courtesy.  He has been very polite to us, too.  Yet something has aroused a suspicion in me that Don Luis Montez wishes to use us in some way that we wouldn’t care to be used.  So I’m saying little, but my eyes are going to be open all the time from now on.”

“Oh, Don Luis must be on the square,” Hazelton retorted.  “What could he want of us that is crooked?”

“I don’t know, yet,” Tom replied, as he led the way rapidly down the road.  “But I’m going to watch, and, if there’s anything wrong, I’m going to get a line on it.”

“El Sombrero is Don Luis’s own mine.  Surely he hasn’t hired us to fool him about his own property.”

“I don’t know what it is that’s wrong,” Tom admitted.  “Nor am I sure that anything is wrong.  But I’m going to do my own watching and gather some of my own information.  See, there are the lights on that trail beyond, and there are several lights.  It looks like a caravan moving down the trail.”

“A caravan?” Harry repeated.  “Of what?”

“I don’t know, Harry.  That’s what I’m here to-night to find out.”

Brisk, soft walking brought them nearer and nearer to the twinkling lights along the trail that ran into their own road at a point lower down.

“I wish I knew what on earth Tom is thinking about,” Harry muttered to himself.  “However, I may as well save my breath just now.  If I hang to him I’m likely to know what it is.”

“We’ll reach a hiding place from which we can watch that caravan, or whatever it is, turn from the hill trail into this road,” Tom whispered, after they had gone somewhat further.

At this point the main road that ran from.  Don Luis’s estate to his mine was decidedly irregular.  Many boulders jutted out, making a frequent change in the course of the road necessary.  It was Tom’s intention to gain the nearest ledge of rock of this sort to the hill trail, and there hide to watch the caravan.

They had nearly reached this point when out of the darkness a figure stole softly to meet them.

“Nicolas!” muttered Tom, in a low voice, all but rubbing his eyes.  “How on earth did you get here?”

“Am I not commanded to keep with you everywhere, and serve you in all things?” demanded the servant.  “Do not go around that next point in the road, caballeros.  If you do, you will run straight into Pedro Gato, who has other men with him.”

CHAPTER VII

DON LUIS’S ENGINEERING PROBLEM

“Gato?” whispered Harry.  “What is he doing around here?”

“There is no reason why we should care what he is doing,” Tom returned.  “He isn’t in the employ of the mine.  Come along, Harry.”

But Nicolas seized the young chief engineer by the arm.

“Beat me, if you will, Senor Americano,” pleaded Nicolas.  “But don’t encounter Gato.  It would be as much as your life is worth.”