It was the door between control cabin and engine room--the door he had just slammed shut. At first nothing was visible; then they saw the van of the enemy that had swarmed through the ship. A thin line of bright yellow color had appeared along the under crack of the door. A second later the door was rimmed on all sides with it. It grew; reached out. Energy flowed through it: fingers of dusty yellow pronged out from the cracks where the door fitted, hung wavering for a moment, melted together, then slumped to the floor to more quickly continue the advance. It increased marvelously, in minor jerks of speed. It was delicate in texture, mold-like. The more there became, the faster it grew: in seconds shreds of it had darted out from the main mass and affixed themselves to the walls and ceiling of the cabin, there to accelerate the horrible filling process. * * * * * All this happened more quickly than it can be related. Within ten seconds most of the cabin was coated by the yellow stuff; grotesquely formed clumps and feathers hung from the ceiling; fern-like fingers kept spurting everywhere. Friday stepped back, before the advance, but not the Hawk. Useless to try and evade the stuff, he knew, and he was fairly positive that there was no immediate danger: the tough fabric of the suits should resist it. A pseudopod-like surge flicked to his leg; crept up; cloaked the suit in patches of yellow; thickened and enveloped him. But it could not pierce through. "Cap'n Carse! Look heah!" He turned to the alarmed voice, brushing light, feathery particles of yellow from his face shield, and found the bulky giant that was Friday a few steps behind him, and pointing mutely at Harkness. The young officer was slumped limply down against a wall, his legs sprawled and body twisted unnaturally. His suit was covered with the yellow, and he had fallen, silently, while they were watching the advance of the fungus and checking the fastenings of their suits. Carse reached him in three steps, stooped, brushed the fungus off the face-shield and peered through. Friday looked over his shoulder. The yellow enemy had laid its deadly fingers on Harkness's fine pale face. Sprouts of yellow trailed from the nostrils; the mouth was a clump of it; tendrils of spongy substance had climbed out the ears and were still threading rapidly over the head, even as the Hawk and Friday watched. "That's how the others died," the adventurer said slowly. "Harkness must have carried a bit of the stuff from aft. It was on him when he put on his suit. At least I hope so. If it can get into these suits...." He left the thought unfinished. "You mean, suh," asked Friday haltingly, "you mean that maybe--maybe it'll get in our suits too?" "Maybe," said Carse without emotion. They waited. CHAPTER IV _The Hawk Prepares a Surprise_