When they do, they wear their own space suits and walk in a file down the street.

Tatiana Petrovna that was the name of the headmistress said that I could leave her there without a worry. Alice also told me not to worry. And I said good-bye to her for the week.

On the third day Alice disappeared.

It was a totally extraordinary event. To begin with, in all the years the boarding school had been in operation it had never lost, or even mislaid, a single child for more than ten minutes. It was totally impossible to get lost in the city on Mars. Let alone an Earth child, in a space helmet. The first Martian who saw him would bring him back to the school. Not to mention the robots. And the police. No, getting lost on Mars is completely impossible. But Alice had done it.

She had been nowhere to be seen for about two hours when I was summoned from the conference and brought to the boarding school in a martian walker. I must have looked utterly distraught when I cycled through the airlock into the dome everyone gathered there froze and were absolutely silent. And just who wasn’t there! All the teachers and the schools robots, the ten Martians in space helmets (they had to wear helmets when they went into the dome where there was an Earth atmosphere) space men, the emergency search team chief Nazaryan, archeologists…

It turned out the city-net and entertainment channels had for the last three hours been broadcasting news that an Earth child had vanished. The whole videophone system was being used to broadcast the emergency. The Martian schools had closed and the school children had gone out in groups combing the city and surroundings…

Alice’s disappearance was noticed as soon as her group returned from its walk. Since then two hours had passed. The oxygen in her helmet was sufficient for three hours.