“How could they?” asked Nisa, hiding the tears that were ready to flow. “Is it as bad as that? The ionisation isn’t so very high.”

“A long time has passed since then,” answered the biologist, glumly. His manly Circassian face with its aquiline nose assumed an expression of sternness, despite his youth. “Radioactive disintegration is dangerous just because it accumulates unnoticed. For hundreds of years the total radiation could increase corns by corus, the unit of radiation; then suddenly there comes a qualitative change, heredity collapses, the reproduction of the species ceases and added to that there are epidemics of radiation diseases. This has happened more than once before, the Circle knows of similar catastrophes.”

“Such as the so-called ‘planet of the lilac sun,’“ came Erg Noor’s voice from behind them.

“Whose sun of spectral class A”, with a light intensity equal to 78 of our suns, provided its inhabitants with very high energy,” added the morose Pour Hyss.

“Where is that planet?” asked Eon Thai, the biologist. “Isn’t that the one the Council intends to colonize?”

“That’s the one, the lost Algrab was named after its star.”

“The star Algrab, that’s Delta Corvi,” exclaimed the biologist. “But it’s such a long way off!”

“Forty-six parsecs. But we’re constantly increasing the power of our spaceship….”

The biologist nodded his head and muttered that it was hardly right to call a spaceship after a star that had perished.

“The star didn’t perish and the planet is still safe and sound. Before another century has passed we shall plant vegetation there and settle the planet,” said Erg Noor with confidence.

He had decided to perform a difficult manoeuvre — to change the ship’s orbit from latitudinal to meridional, sending the ship along a north-south line parallel to the planet’s axis of rotation. How could they leave the planet until they were sure that there were no survivors? It might be that survivors were unable to communicate with the spaceship because power installations had been wrecked and instruments damaged.

This was not the first time Nisa had seen her commander at the control desk in a moment of great responsibility. With his impenetrably expressionless face and his abrupt but always precise movements he seemed like a hero of legendary times to the auburn-haired astronavigator.

Again Tantra continued her hopeless journey round Zirda, this time from pole to pole. In some places, especially in the temperate latitudes, there were wide belts of bare earth, a yellow haze hung over them and through it, from time to time, appeared the lines of gigantic red dunes from which the wind sent up clouds of sand.

Then again came the funereal pall of black velvet poppies, the only plant that had withstood radioactivity or had produced a mutation of its species viable under irradiation.

The whole picture was clear. It was not only useless, it was even dangerous to search for supplies of anameson that had, on the recommendation of the Great Circle, been laid in for visitors from other worlds (Zirda had no spaceships of her own, only planetships). Tantra began slowly unwinding the spiral away from the planet. She gained a velocity of 17 kilometres a second using her ion trigger motors, the planetary motors that gave her speed enough for trips between adjacent planets and for taking off and landing, and drew away from the dead planet. Tantra turned her nose towards an uninhabited system known only by its code name where bomb beacons had been thrown out and where Algrab should have awaited her. The anameson motors were switched on and in fifty-two hours they accelerated the spaceship to her normal speed of 900,000,000 kilometres an hour. Fifteen months’ journey would take them to the meeting place — eleven months of the dependent time of the ship — and the whole crew, with the exception of those on watch, could spend that time in sleep. A month, however, passed in discussion, in calculations and in the preparation of a report for the Council. From reference books it was discovered that risky experiments had been made on Zirda with partially disintegrating atomic fuels. They found references to statements by leading scientists who warned the people that there were symptoms of the adverse biological effect of the experiments and demanded that they be stopped.

A hundred and eighteen years before a brief warning had been sent through the Great Circle; it would have been sufficient for people of the higher intellectual categories but apparently it had not been treated seriously by the government of Zirda.

There could be no doubt that Zirda had perished from an accumulation of harmful radiations following numerous careless experiments and the reckless use of dangerous forms of nuclear energy instead of wisely continuing the search for other, less harmful sources.

The mystery had long since been solved, twice the spaceship’s crew had changed their three months’ period of sleep for normal periods of activity of the same length.

Tantra had been circling round the grey planet for many days and with each passing hour the possibility of meeting Algrab grew less and less. Something terrible loomed ahead.

Erg Noor stood in the doorway with his eyes on Nisa as she sat there in meditation — her inclined head with its cap of thick hair like a luxuriant golden flower, the mischievous, boyish profile, the slightly slanting eyes that were often screwed up by restrained laughter and were now wide open, apprehensively but courageously probing the unknown…. The girl did not realize what a tremendous moral support her selfless love had become for him. Despite the long years of trial that had steeled his willpower and his senses, he sometimes grew tired of being commander, of having to be ready at any moment to shoulder any responsibility for the crew, for the ship and for the success of the expedition. Back there on Earth such single-handed responsibility had long since been abandoned — decisions there were taken collectively by the group of people who had to carry them out. If anything unusual occurred on Earth you could always get advice, and consultations on the most intricate problems could be arranged. Here there was nobody to turn to and spaceship commanders were granted special rights. It would have been easier if such responsibility had been for two or three years instead of the ten to fifteen years that were normal for space expeditions! Erg Noor entered the control tower.

Nisa jumped up to meet him. “I’ve got all the necessary material and the charts,” he said, “we’ll start the machine working!”

The commander stretched himself in his armchair and slowly turned over the thin metal sheets he had brought, calling out the numbers of coordinates, the strength of magnetic, electric and gravitational fields, the power of Cosmic dust streams and the velocity and density of me-teoroid streams. Nisa, all her muscles tensed with excitement, pressed the buttons and turned the knobs of the computing machine. Erg Noor listened to a series of answers, frowned and lapsed into deep thought.

“There’s a strong gravitational field in our way, the area in the Scorpion where there is an accumulation of dark matter near star 6555 CR+11 PKU,” began Noor. “We can save fuel by deviating this way, towards the Serpent. In the old days they flew without motors, using the gravitational fields as accelerators, along their edges.” “Can we do the same?” asked Nisa.

“No, our spaceships are too fast. At a speed of 5/6ths of the absolute unit or 250,000 kilometres a second our weight would be 12,000 times greater in a field of gravitation and that would turn the whole expedition into dust. We can only fly like this in the Cosmos, far from large accumulations of matter. As soon as the spaceship enters a gravitational field we have to reduce speed, the stronger the field the more we must reduce.”