In any case, I always enjoyed walking out in the open on the moon. It was not merely the scenery, which even at its most awe-inspiring one can grow accustomed to after a while. No—what I never tired of was the effortless, slow-motion way in which every step took me bounding over the landscape, giving me the freedom that before the coming of space flight men only knew in dreams.

We had done the job and were halfway home when I noticed a figure moving across the plain about a mile to the south of us—not far, in fact, from the Russian base. I snapped my field glasses down inside my helmet and took a careful look at the other explorer. Even at close range, of course, you can’t identify a man in a space suit, but because the suits are always coded by colour and number that makes no practical difference.

“Who is it?” asked Henderson over the short-range radio channel to which we were both tuned.

“Blue suit, Number 3—that would be Surov. But I don’t understand. He’s by himself.”

It is one of the most fundamental rules of lunar exploration that no one goes anywhere alone on the surface of the moon. So many accidents can happen, which would be trivial if you were with a companion—but fatal if you were by yourself. How would you manage, for example, if your space suit developed a slow leak in the small of the back and you couldn’t put on a repair patch? That may sound funny; but it’s happened.

“Perhaps his buddy has had an accident and he’s going to fetch help,” suggested Henderson. “Maybe we had better call him.”

I shook my head. Surov was obviously in no hurry. He had been out on a trip of his own, and was making his leisurely way back to the Ziolkovski. It was no concern of mine if Commander Krasnin let his people go out on solo trips, though it seemed a deplorable practice. And if Surov was breaking regulations, it was equally no concern of mine to report him.