Then, without warning, something went wrong with the inner workings of 12W-62's metal cube so that he suffered lapses of control. He kept on going when he should have stopped, and sometimes he stopped entirely and seemed to have no ability to move again. These periods of inactivity, brief at first, became prolonged. The machine men knew the symptoms and were not surprised when the inevitable happened. The mechanism of 12W-62 went entirely dead! The excessive requirements of Ajiat had exhausted his energy supply which could only be recharged at the spaceship. There was only one thing to do, which they accomplished with as little loss of time as possible. They removed the head of 12W-62 from his useless body and carried it with them. 29G-75 was quickly outfitted with one of the metal legs, and they carried the other three with them in case of emergency. The race against time tightened. Their slight advantage had been lost. Professor Jameson kept the doubts in his mind hidden from his companions. They were nearly to the foot of the mountain, and the distance from there to the spaceship was well within a day's walk. They gained level ground shortly before dawn. They had covered less than a mile of distance when 6W-438 fell over suddenly and could not rise. More time was lost in removing his head. As dawn broke, Professor Jameson collapsed, and even as 29G-75 stooped to help him and ascertain the extent of his trouble, he, too, lost his ability to move! He stood quiet and useless on his four metal legs above the fallen body of the professor. Each of the two machine men carried the head of a companion. "This looks to be the end," said 6W-438. "We still have today. Shortly after dark, if our calculations are not wrong, the nova will take place." The sky above them grew brighter. Idle and impassive, they watched the birds commencing to fly far up the side of the nearby mountain. The sun, that dangerous furnace which was destined to explode before another full rotation of Ajiat, crept over the horizon. Doom shone upon the machine men. Somewhere not far from that flaming, incandescent mass, the vast conglomeration of meteoric fragments sped like a racing powder train on a grim errand to purge all the worlds of that system of life, spreading an all-destroying heat wave to the outermost realms of the farthest orbit with the speed of light. A small swarm of birds caught their attention. The Quari had evidently sighted them and were descending to investigate. "This time they will find no resistance," said the professor. "Do you think they will carry us away?" "It is doubtful--when they find that we are not good to eat." The birds were acting strangely, as if they were fighting over something among themselves. Their manner of descent was strange, too. The machine men had never seen them come down so directly before. Generally, they flew down in long, swinging loops. This time, their turns were shorter and took less distance.