Like a dark mouth set in the white face of the windowless tower gloomed a gate of shadows, open to the square. That yawning space was black with emptiness. There were no doors hung on hinges; only that sombre opening, silently menacing. Kortha stood looking at it. The wind ruffled the white fur of his mantle. It stirred his amber hair and cooled the naked skin of arms and shoulders. He lifted his hammer and shook it in the sunlight, and grinned. He walked forward. Xax spoke to him above the clicking of his needles on the broken flagging of the square, "Are you walking into that thing like a _yavit_ to the trap?" "Others have examined it before me, Xax. I have not heard that their examinations saved them. Besides, if the death that lurks in the tower of Zut still lives, I have no need to fear Guantra." They were quite close to the doorway now, and looking in they glimpsed something white and shining on the tiled floor. As they drew nearer, the heaps of white stuff grew plainer. They were bones. Human bones: what was left of the skeletons of many men. Kortha lifted his head to survey the doorway. His green eyes blazed with challenge, but their fire was controlled, and alert. He saw the entrance plain and severe in style, affording no clue as to the manner of its deadliness. From the way in which the walls shone, so clearly translucent with the hint of inner fires deep within them, he knew that the tower was built of _transvaline_, that rare building material whose secret was lost with so many others during the Great War. In the walls two tall, faint strips of black shone dully: the doors of this queer adit. Kortha swung his hammer in his hand and tossed it through the opening. The doors remained open, and the bolt of force that he half expected to sweep from somewhere at the hammer, remained hidden. He grunted to Xax, "Come on. No sense wasting time out here, like dogs fretting before a bear's cave." They passed the threshold together, and stood in a domed chamber, circular in shape, with another doorway beyond and opposite the entrance. There were words on the lintel above its arch. "Science chamber," whispered Kortha, and started toward it. Behind them was a metallic whisper, susurrating in the stillness. Kortha whirled and cursed and leaped. The doors closed before his shoulder struck their smooth black surface. He hit and bounced slightly, jarred. Kortha swore slowly, fluently, looking at the doors. "How long will the air last?" wondered Xax. "Longer than our bellies will stand the lack of food and drink. So this is the great tower of Zut. Sliding doors that imprison any who break a secret electri-beam. Zut! I'd thought better of the Ancient Ones. This is really too simple. Find the beam and send a current along it, and the doors'll open again." Kortha swung on his heel, going down the hall and into the Science Chamber. Standing motionless on the threshold, he ran keen eyes into the huge chamber.