"We will stay here," he told the others, "until we are ready to attack the Oan." "But there are only six of us," one of the white men protested. "There are hundreds of the beasts. We wouldn't have a chance." Ro smiled. "We will speak of that when it is dawn again," he said with his thoughts. "Now we must rest." He sat in a corner of the cave and leaned back against the wall. His eyes were half shut and he pretended to doze. Actually he was studying the white ones. The man with the silver hair seemed very old and weak, but very wise. The other men had hair as black as any Martian's, but their skin was pure white. They were handsome, Ro thought, in a barbaric sort of way. One was lean and determined, the other, equally determined, but stouter and less impressive. Ro then centered his attention on the girl. Her golden hair gleamed proudly, even in the dusk. She was very beautiful, almost as lovely as Na. "Tell me," he asked suddenly, "where is this strange place you come from? And how is it that you can speak and cause others to speak with their minds?" It was the old man who answered. "We come from a place called Earth, many millions of miles away through space. My daughter, Charlotte, my two assistants, Carlson--" the lean man nodded--"Grimm--" the stouter man acknowledged the introduction--"and myself are an expedition. We came here to Mars to study." Ro introduced himself and Na. "What manner of a place is this Earth?" he asked, after the formalities. "Our part of Earth, America, is a great country. Our cities are built of steel and stone, and we travel about in space boats. Now tell me, what is it like here on Mars? Surely the whole planet isn't wilderness. What year is it?" "You have seen what it is like here," Ro answered. "As for 'year,' I don't understand." "A year is a measure of time," the old man explained. "When we left Earth it was the year twenty-two hundred." "We have nothing like that here," said Ro, still puzzled. "But tell me, about this speaking with the mind. Perhaps I shall understand that." "It's simple telepathy. We have mastered the science on Earth. It takes study from childhood, but once you have mastered the art, it is quite simple to transmit or receive thoughts from anyone. A mere matter of concentration. We--who speak different tongues--understand each other because of action we have in mind as we speak. We want the other to walk, we think of the other walking. A picture is transmitted and understood. It is a message in a Universal language." Ro sighed. "I am afraid we are very backward here on Mars," he said wearily. "I would like to learn more, but we must sleep now. Tomorrow will be a very busy day." Ro slipped his arm about Na's shoulder and drew her closer. With their heads together they slept. * * * * * Ro awakened with the dawn. He was startled to find that Na had left his side. He rose quickly and strode to the mouth of the cave.