Nellon squinted. Gradually he began to make out details. The strange surface revealed by the slide seemed to have the mellow hue of bronze, but Nellon could not be sure, since it was queerly dappled and flecked with tones of gold and red. He thought it must be from the strain on his eyes, and closed them momentarily. But when he looked again the colors were as weird as he had last seen them. This time, however, he made out a detail which he had missed previously. The surface seemed to be crossed by a black line or stripe. "Now what in the world can that be?" Tim Austin's voice was wondering, vaguely troubled. "It's like no sample of rock or soil we've taken. Metal--that's what it is!" he exclaimed of a sudden. "It's an exposed vein of some metal. Come on, Brad, let's have a look at it." Nellon got to his feet, his eyes fixed upon that uncanny patch of something which stood out against the surrounding whiteness like a smear of blood. Big Tim was already started up the bank. Nellon sucked in a breath and followed after him. * * * * * The climb was a hard and difficult one, and their recent physical jarring caused by the fall made it all the harder. But curiosity pulled them on like a vast magnet. In the exertion they forgot their aches and bruises. Slipping and sliding, clutching for handholds, floundering in loose drifts which filled pockets of hardened crust, they made their way slowly but surely up the bank. Finally they stood before that strangely mottled patch of red and brown and gold. The mood of awed wonder which gripped them at once heightened and deepened. "It _is_ metal!" Tim Austin breathed. "But--but, Brad, it's not a vein. It's--" "It's a door!" Nellon finished hoarsely. It was a door, a metal door in the snow covered bank of a falls that had, in some long, long ago, solidified to ice. A door to what? Where did it lead? What would be on the other side of it? What could be on the other side of a metal door on a world where it was doubtful that living beings had ever existed at all? There was a rasp in Nellon's earphones. And then Big Tim Austin's voice followed it. "Brad--I'm going in. This--why, this is the biggest find of the whole expedition!" "It might be dangerous," Nellon pointed out, before he could become aware of the wealth of irony which lay behind the words. "We don't know what sort of life--" "But this door has been hidden under snow for the Lord only knows how many years, Brad. Look where the crust had split here. It's thick, thick. Nothing has gone in or out for a hell of a long time. If there were beings, they're either gone or dead."