The Pony Rider Boys and their outfit had arrived that afternoon, and during the remaining hours of daylight they had been excitedly exploring the ancient dwellings, most of which were in a dilapidated condition.  There was one, however, two stories in height, that was in an excellent state of preservation.  In fact it appeared as if it had only recently been vacated.  After an examination of all the ruins Mr. Marquand had discovered what led him to believe that this was the structure which the old Pueblo chief referred to in his description of the resting place of the treasure.  The chief had said he had never been near the spot.  He was the only member of his tribe to whom the secret had been handed down, and he in turn had transmitted it to the white man who now stood within the shadow of the ancient dwelling place.

“I have my reasons for believing this is the place,” answered Mr. Marquand, in response to the Professor’s question.  “If I am wrong, we shall have to wait until the moon rises to-morrow night.  Come inside now, and we will close the door.”

All hands crowded into the cool chamber, closing the heavy wooden door that barred the entrance.

“Don’t see how moonlight can get through solid walls,” muttered Stacy.  “Ought to leave the door open.”

No one answered him.  In the darkened chamber, with its peculiar, musty odors, the boys did not feel in the mood for hilarity or even for speech.  There was something about their situation that seemed to impress them profoundly.

“Stand over against the wall on the side, so as not to obstruct any light that might possibly get in here,” directed Mr. Marquand.

The others moved silently to the side of the room indicated by him.  They had stood thus for fully five minutes when an exclamation from Stacy broke the stillness harshly.

“Look!  Look!” cried the fat boy.

A slender shaft of light had suddenly pierced the blackness, coming they knew not whence.  It was there.

“Must be a pin hole through the wall up near the ceiling,” suggested Kris Kringle.

The silver thread shot across the chamber, ending abruptly on the adobe floor some three feet from the back wall.

“That’s the spot!” shouted Mr. Marquand triumphantly.

He threw himself on the floor, and with his knife scratched a cross on the spot where the moonbeam rested.  Scarcely had he done so when the delicate shaft of light disappeared as suddenly as it had come.

“It’s gone,” breathed the boys.

“But it has pointed the way.”

“And we have followed the silver trail to its end,” added Ned Rector poetically.

“Bring the tools!” cried Mr. Marquand.

While they were doing so, he struck a match and lighted the lantern that they had brought with them from their camp in the foothills.  His first care was to bar the door with the heavy wooden timber that he had cut and which he now slipped into its fastenings.