“I have landed on Phobos and am being attacked by a Z-class cruiser. Think I can hold out until you come, but hurry.”

The message wasn’t even in code, and it left Commander Smith a sorely puzzled man. The assumption that K.15 was still aboard the ship and that the whole thing was a ruse was just a little too naive. But it might be a double-bluff: the message had obviously been left in plain language so that he would receive it and be duly confused. He could afford neither the tune nor the fuel to chase the scout if K.15 really had landed. It was clear that reinforcements were on the way, and the sooner he left the vicinity the better. The phrase “Think I can hold out until you come” might be a piece of sheer impertinence, or it might mean that help was very near indeed.

Then K.i5’s ship stopped blasting. It had obviously exhausted its fuel, and was doing a little better than six kilometres a second away from the sun. K.15 must have landed, for his ship was now speeding helplessly out of the Solar System, Commander Smith didn’t like the message it was broadcasting, and guessed that it was running into the track of an approaching warship at some indefinite distance, but there was nothing to be done about that. The Doradus began to move towards Phobos, anxious to waste no time.

On the face of it, Commander Smith seemed the master of the situation. His ship was armed with a dozen heavy guided missiles and two turrets of electromagnetic guns. Against him was one man in a space suit, trapped on a moon only twenty kilometres across. It was not until Commander Smith had his first good look at Phobos, from a distance of less than a hundred kilometres, that he began to realize that, after all, K.15 might have a few cards up his sleeve.

To say that Phobos has a diameter of twenty kilometres, as the astronomy books invariably do, is highly misleading. The word “diameter” implies a degree of symmetry which Phobos most certainly lacks.