Back in the 1950s, I wrote a series of six derring-do novels about David "Lucky" Starr and his battles against malefactors within the Solar System. Each of the six took place in a different region of the system, and in each case I made use of the astronomical facts-as they were then known.

Now, more than a quarter-century later, these novels are being published in new editions; but what a quarter-century it has been! More has been learned about the worlds of our Solar System in this last quarter-century than in all the thousands of years that went before.

DAVID STARR: SPACE RANGER was written in 1951 and at that time,there was still a faint possibility that there were canals on Mars, as had first been reported three-quarters of a century earlier. There was, therefore, a faint possibility that intelligent life existed there, or had existed at one time.

Since then, though, we have sent probes past Mars and around it to take photographs of its surface, and map the entire planet. In 1976, we even landed small laboratories on the Martian surface to test its soil.

There are no canals. There are instead, craters, giant volcanoes and enormous canyons. The atmosphere is only 1 percent as dense as Earth's and is almost entirely carbon dioxide. There is no clear sign of any life at all upon Mars, and the possibility of advanced life upon it, now or ever, seems nil.

If I had written the book today, I would have had to adjust the plot to take all this into account.

I hope my Gentle Readers enjoy the book anyway, as an adventure story, but please don't forget that the advance of science can outdate even the most conscientious science-fiction writer and that my astronomical descriptions are no longer accurate in all respects.

Isaac Asimov

David had been waiting patiently for Dr. Henree and, in the meanwhile, enjoying the atmosphere of International City's newest restaurant. This was to be his first real celebration now that he had obtained Ms degree and qualified for full membership in the Council of Science.

He did not mind waiting. The Cafe Supreme still glistened from the freshly applied chromosilicone paints. The subdued light that spread evenly over the entire dining room had no visible source. At the wall end of David's table was the small, self-glowing cube which contained a tiny three-dimensional replica of the band whose music filled in a soft background. The leader's baton was a half-inch flash of motion and of course the table top itself was of the Sanito type, the ultimate in force-field modernity and, except for the deliberate flicker, quite invisible.

David's calm brown eyes swept the other tables, half-hidden in their alcoves, not out of boredom, but because people interested him more than any of the scientific gadgetry that the Cafe Supreme could gather. Tri-television and force-fields were wonders ten years before, yet were already accepted by all. People, on the other hand, did not change, but even now, ten thousand years after the pyramids were built and five thousand years after the first atom bomb had exploded, they were still the insoluble mystery and the unf aded wonder.

There was a young girl in a pretty gown laughing gently with the man who sat opposite her; a middle-aged man, in uncomfortable holiday clothing, punching the menu combination on the mechanical waiter while his wife and two children watched gravely; two businessmen talking animatedly over their dessert.

And it was as David's glance flicked over the businessmen that it happened. One of them, face congesting with blood, moved convulsively and attempted to rise. The other, crying out, stretched out an arm in a vague gesture of help, but the first had already collapsed in his seat and was beginning to slide under the table.

David had risen to his feet at the first sign of disturbance and now his long legs ate the distance between the tables in three quick strides. He was in the booth and, at a touch of his finger on the electronic contact near the tri-television cube, a violet curtain with fluorescent designs swept across the open end of the alcove. It would attract no attention. Many diners preferred to take advantage of that sort of privacy.

The sick man's companion only now found his voice. He said, "Manning is ill. It's some sort of seizure. Are you a doctor?"

David's voice was calm and level. It carried assurance. He said, "Now sit quietly and make no noise. We will have the manager here and what can be done will be done."

He had his hands on the sick man, lifting him as though he were a rag doll, although the man was heavyset. He pushed the table as far to one side as possible, his fingers separated uncannily by an inch of force-field as he gripped it. He laid the man on the seat, loosening the Magno-seams of his blouse, and began applying artificial respiration.

David had no illusion as to the possibility of recovery. He knew the symptoms: the sudden flushing, the loss of voice and breath, the few minutes' fight for life, and then, the end.

The curtain brushed aside. With admirable dispatch the manager had answered the emergency signal which David had tapped even before he had left his own table. The manager was a short, plump man, dressed in black, tightly fitting clothing of conservative cut. His face was disturbed.

"Did someone in this wing- " He seemed to shrink in upon himself as his eyes took in the sight.

The surviving diner was speaking with hysterical rapidity. "We were having dinner when my friend had this seizure. As for this other man, I don't know who he is."

David abandoned his futile attempts at revival. He brushed his thick brown hair off his forehead. He said, "You are the manager?"

"I am Oliver Gaspere, manager of the Cafe Supreme," said the plump man bewilderedly. "The emergency call from Table 87 sounds and when I come, it is empty. I am told a young man has just run into the booth of Table 94, and I follow and find this." He turned. "I shall call the house doctor."

David said, "One moment. There is no use in that This man is dead."

"What!" cried the other diner. He lunged forward, crying, "Manning!"

David Starr pulled him back, pinning him against the unseeable table top. "Easy, man. You cannot help him and this is no time for noise."

"No, no," Gaspere agreed rapidly. "We must not upset the other diners. But see here, sir, a doctor must still examine this poor man to decide the cause of death. I can allow no irregularities in my restaurant."

"I am sorry, Mr. Gaspere, but I forbid the examination of this man by anyone at the moment."

"What are you talking about? If this man dies of a heart attack____________________ "

"Please. Let us have co-operation and not useless discussion. What is your name, sir?"

The living diner said dully, "Eugene Forester."

"Well, then, Mr. Forester, I want to know exactly what you and your companion ate just now."

"Sir!" The little manager stared at David, with eyes swelling out of their sockets. "Are you suggesting that something in the food caused this?"

"I'm not making suggestions. I'm asking questions."

"You have no right to ask questions. Who are you? You are nobody. I demand that a doctor examine this poor man."

"Mr. Gaspere, this is Council of Science business."

David bared the inner surface of his wrist, curling the flexible Metallite sleeve above it. For a moment it was merely exposed skin, and then an oval spot darkened and turned black. Within it little yellow grains of light danced and flickered in the familiar patterns of the Big Dipper and of Orion.