“Then another time, my dear fellow, for here comes Don Luis, and I see Dr. Tisco returning from the garden.”

That forestalled conversation for the time being.  When the young engineers, still relentlessly attended by Nicolas, sought their own rooms Hazelton was so drowsy that he undressed hurriedly and dropped into bed.

Later in the night Harry sat up suddenly in the dark.  Some one was moving in the parlor that separated the two bedrooms.  An instant after awakening Harry slipped off the bed, then stole toward the next room.

In the darkness he made out a moving figure.  Like a panther Harry sprang, landing on the all but invisible figure.

“Now, I’ve got you!” Hazelton hissed, wrapping his arms around the prowler.

“And small credit to you,” drawled Tom’s dry voice.  “Hist!”

“What’s up?” demanded Hazelton, dropping his voice to a whisper.

“You and I are.”

“But what’s the matter?”

“I couldn’t sleep,” Tom whispered.

“You—­troubled with nerves!” gasped Hazelton.

“Not just the way you understand it,” returned Tom.  “But I was thinking, thinking, and I sat by the window yonder.  Come over there, Harry, but step without noise.”

Wondering what it all meant, Hazelton softly followed his chum to the open window.

“Now, look,” said Tom, pointing, “and tell me what you see.”

“A moment ago I thought I saw a light twinkling over there among the hills.”

“Look sixty seconds longer, and you’ll see more lights, Harry; those lights are on the trail that leads from the nearest gold mines to El Sombrero.  It is the trail Don Luis pointed out to us to-day.”

“But what—­”

“Harry, I’m going to get on my clothes and slip over in that direction.  Do you want to go with me?”

“Yes; but what—­”

“I can tell you better when we’re on the way.  Come on; dress!  We can easily leave the house without being detected.”

Though Harry had already been through hosts of adventures, he felt creepy as he dressed with speed and stealth, bent on slipping unobserved out of their employer’s house.  But he was used to following his chum’s lead.

When both were ready, which was very soon, Tom softly opened the door of their parlor, thrusting one foot out into the broad corridor.  As he did so he kicked against a man lying prostrate on the floor.  It was Nicolas, the Mexican attendant, sleeping across their threshold that he might be on hand when wanted.

The man stirred, muttered something almost inaudible, then gradually began to breathe more deeply.  Tom, after waiting, took a step over the body of Nicolas.  Harry closed the door behind them, then followed.  Soon after they stood out on the lawn.

“I’m glad Nicolas went to sleep again,” muttered Tom, in a low voice.  “The fellow would have insisted on following us, and I wouldn’t want him with us to-night, to tell Don Luis everything.”