Again he watched one of the smaller ones intently, noticing how it grew. Jon walked about, looking at the different structures of that mysterious, growing crystal. Suddenly he stiffened, straining, listening. Then he called, "Hey, Jak, you hear anything?" "Huh?" his brother tore his gaze from the crystallization he was watching. "Hear what?" "Turn up the power of your suit receiver. There. There it is again.... Hey, sounds like our siren!" "Yes, I heard it then. Mother must be in trouble, or something." Jak's last words were flung back across his shoulder as he ran as fast as he could across the icy wastes of the valley floor. Nor was Jon far behind. In fact, after a few strides the younger, but longer-legged boy was beside him, then forged ahead. "Hurry, Owl! Mom wouldn't signal unless it was urgent." "Maybe Father's worse." They tried to conserve their breath after that for running and climbing. Once Jon broke the silence. "Turn your oxygen a little higher, Jak," he said as he twisted the small lever at his own shoulder to increase the flow of the strength-giving energy. They were panting and winded by the time they reached the top of the hill. But they disregarded fatigue in the face of their mother's probable danger--or their father's. Jon looked quickly to one side and then the other. As Jak topped the ridge he saw his brother run some twenty feet or so to where he had spotted a fairly smooth downward slope. Down this the younger boy launched himself feet first, sliding on his suit's back. Jak instantly realized the reason, and threw himself after his brother. In less than a tenth of the time it would have taken them to climb down, the boys were at the foot of the hill. They struggled to their feet and started off toward the ship. Both were again shaken and sorely bruised from their rough slide, but they trotted on. Mother had called--nothing else mattered. As they came closer to the ship they saw her reason for summoning them. All about the outer lockdoor were those strange crystalline structures, growing swiftly. As the two boys came still closer, they could see that streamers of the crystals had already reached the lower edge and were trying to force their way through the almost imperceptible crack. "They'll never get ... through there," Jon panted as he raced the last few feet. "Don't see ... how they can ... but watch 'em." Jak waded into the alien, growing things. His gloved fists smashed right and left as he spoke. Jon was already doing the same. But whether these crystal-beings were of a different type from those that Jak had broken in the distant valley, or just what was the reason, the boys now found it more difficult to break these crystals down. "These aren't ... like those ... back there." Jon had now seen that these crystals did not always grow in pyramidal shape.