"Just that there'd been a nuclear explosion of unknown origin. They said there was something spectacular about it."

"Spectacular? Si! Your government was gracious enough to accept our request for technical help without demanding details. Security is very difficult, as you comprehend." Brulieres looked absent for a moment. "The explosion occurred at a spot famous in pre-Christian legends, which is why friend Dientes accompanies us. He is considered experto." The intense eyes turned upon the Indian, with a hint of mischief. "Not that he fails to be a good Christian as well."

The Indian crossed himself nervously.

"The explosion," Brulieres went on, "seems to have uncovered some very ancient tunnels. We wish to explore them, but we felt we needed a nuclear physicist along. Especially since there appears the possibility that the explosion originated from the tunnels."

Craig heard Noriega clear his throat. Brulieres glanced at Noriega. "It has also been suggested," the priest said, "that the uncovering of the tunnels is coincidental, and that the explosion was of foreign origin."

Craig thought that over, and was annoyed. "That does not seem likely," he said, a little stiffly. "Nobody is tossing live warheads around."

Noriega spoke for the first time. His voice was crisp and rather high. "You can perhaps speak for your own nation, Doctor Craig; but others too possess missiles."

Brulieres interposed, "You no doubt know, Doctor, that a communist putsch very nearly took over this country. The present government has been compelled to very strict measures against a further attempt. Therefore we are not popular with the communist nations."

Craig waved a hand impatiently. "Yes, I know that, but...." He realized he was being careless. "I only wish to approach my investigation with an open mind. You say the tunnels were ancient? Incan, perhaps?"

Brulieres shook his head slowly. "They were hardly capable of anything on this scale. One cannot speak so surely of those who preceded the Incas in this place."

Craig pondered, and felt his pulse move faster. "How much have you learned so far?"

"What can be seen from the air. We will be the first to land, if you decide it is safe."

II

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