swirling to the left, and Leah's to the right, one girl the mirror image of the other.

But the Leah sitting before him now was thin and tired-looking, her sallow skin was lined, and her soft voice had become vinegary with disappointments. Her red hair had faded to a commonplace brown, and the white streak in the center was yellowed. An unwanted, souring old maid. But there was only one response to make.

"You look fine to me, Leah," he said. "What time did you say your sister is coming?"

"Tomorrow evenings' Playground Jet. Why?"

"We'll have to think of a way to celebrate. But right now, I'd like to get started on my new paper. I've got to meet Dr. Haslam before long."

"I know." She raised her faded gray eyes. "That was a funny thing you said to him just now over the intercom. You said to him it was getting late. But it isn't late. It's only eleven o'clock in the morning."

David stared. "Do you mean to say you were listening to our conversation? Why did you do that?"

She fidgeted and turned away from him. "Oh, I just happened to be at Comdesk and I guess the circuit wasn't closed. Does it matter? But it seemed a funny thing for you to say."

"People in Office Category are not supposed to understand Research," he said severely. "If they were capable of Research, Leader Marley's planners would have placed them there. As for its being late, it is, as far as White Martian Fever is concerned. Which is the subject of my paper. Prepare to take dictation."

Shrugging her shoulders, she poised her bony fingers over the keys of the little machine.

"Paper for delivery at the Summer Seminar," he began.

"But, Dr. Wong, that doesn't have to be ready for three months yet!"

"Miss Hachovnik! Please remember Leader Marley's Maxim: Individuals born into Office Category are the bone and muscle of the State; Nature has designed them to act, not to think."

"Yes, Dr. Wong. I'm sorry."

"Don't worry, Leah. We're old friends, so I won't report you. All set?"

He took a pencil from his leather case and tapped it against his notebook as he ruffled the pages, wondering how to begin. It was hard to think logically when a part of his mind was in such confusion. Had Leah been listening in to all of his phone conversations? If so, it was fortunate that he had long ago devised an emergency code. Was it only idle curiosity that had prompted her or was she acting under orders? Was anyone else watching him, he wondered, listening to his talk, perhaps even checking the routine of his experimental work? There was Lanza this morning—why had he come unannounced, in person, when a Communications call would have served the purpose equally well?

Leah's voice broke in. "I'm ready, Dr. Wong."

He cleared his throat. "...the Summer Seminar. Title: The Propogation of White Martian virus. Paragraph. It will be remembered that the early attempts to establish Earth colonies on Mars were frustrated by the extreme susceptibility of our people to two viruses native to the foreign planet, viruses which we designate as Blue Martian and White Martian, according to the two distinct types of fever which they cause. Blue Martian Fever in the early days caused a mortality among our colonists of nearly eighty-five per cent, and made the establishment of permanent colonies a virtual impossibility.

"Under the inspired leadership of Leader Marley and with the advice of his deputy Dr. Lanza, this laboratory in Research worked out a method of growing the virus and producing an immunizing agent which is effective in nearly all human beings. Only the cooperation of several Categories made possible such a feat. It will not be forgotten that even the humblest helpers in the Institute had their share in the project, that some of them acted as human volunteers in the experiments, well knowing the risks they ran, and were afterward rewarded by a Free Choice.

"One person in Office Category, for instance, was given the privilege of learning to play the flute, although nobody in his family had ever belonged to Music, and another person in Menial Category was permitted a month's study of elementary algebra, a nearly unheard of indulgence for a person in his position. But as Leader Marley so graciously remarked in conferring the awards: To the individual who risks much, the State gives much."

"Like me and Tanya?" the girl asked, stopping her typing.

"Yes, like you and Tanya. You were allowed to act a part in an amateur Theater group, I remember, and since Tanya was made too ill to be able to use a Free Choice, she was sent out west to the Playground, just as though she had belonged to Ruler Category. Now where was I?"

"'The State gives much.'"

"Oh, yes. Paragraph. Since the discovery of the immunizing mechanism to Blue Martian, permanent colonies have been established on Mars. But there remains the more elusive problem of White Martian Fever, which, though its mortality is only thirty per cent, is still so crippling to those victims who survive that the Martian colonies cannot begin to expand, and the resources of the planet cannot be fully developed, until an immunizing agent is found.

"For the past eight years this laboratory has been working at the problem, among others, and we are now in a position to report a small degree of progress. Since it proved to be impossible to grow the virus in the usual media, it occurred to us—"

The intercom buzzed, and Dr. Wong turned away to open the dial.

"David? What's happened to you? I've been waiting here in the lab a quarter of an hour."

"Sorry, Karl. I thought I had more time. Be right down."

He reached for his white lab coat and shoved his long arms into the starched sleeves. "That's all we have time for now, Leah. Can you get an early lunch and be back here this afternoon at two?"

But she was not listening. She was leaning over to look at the desk, staring avidly at the open pages of Dr. Wong's notebook. Without comment he picked up the book, closed it, put it in the top drawer and locked the drawer. She watched him with curious eyes.

"What funny marks those were, Dr. Wong! Do you keep your notes in a private system of shorthand?"

"No. I write them in Coptic. For the sake of privacy."

"What's Coptic?"

"A dead language, spoken by the ancient Egyptians thirty or forty centuries ago."

"But you're Research, not Linguistics! It's against the law for you to know other languages. Are you a traitor?"

"My dear Leah," he said, "I'm far too sensible a man to go in for bootleg study, to learn anything without permission. I have no wish to end up with a pick-ax in my hands. But you shouldn't tax your little mind with thinking. It's not your job. You're not equipped for it, and it's dangerous."

David passed the watchguard stationed in the basement corridor, walked through the open door of the laboratory, past the bench where a row of pretty technicians sat making serial dilutions of bacterial and virus suspensions, through the glow of the sterilizing room, and on into the small inner lab where flasks of culture media and developing hens' eggs sat in a transparent incubator, and petri dishes flecked with spots of color awaited his inspection.

Dr. Karl Haslam was standing at the work bench, with a pair of silver forceps which held a small egg under the psi light. Gently he lowered the egg into its warm observation chamber, covered the container, and sat down.

"Well, here I am. What's gone wrong? Explain yourself, my boy."

"Just a minute." Grinning maliciously, David took down a bottle from the shelf of chemicals, poured a colorless liquid into a beaker, and walked casually toward the doorway as he agitated the mixture of hydrogen sulphide and mercaptans. He held his breath, then coughed, when the fumes of putrescence filled the room and drifted out the door. He looked into the technician's room.

"Sorry for the aroma, girls, but this is a vital experiment."

"Can't you at least shut the