They advanced cautiously into the hall, disturbing a bat which circled eerily around and around the light. Nesbit flinched each time it swooped close. "Nasty beast!" Matt didn't reply, his eyes searching out the dusty walls for a stairway. "There." He pointed with his rifle. The door stood open. Stairs descended into blackness. The fort proved to have not one basement, but three. The first level held trucks, tanks, half-tracks, and cars in solid ranks. The second basement was stored with ammunition, the third held furnaces, a pumping system and a power plant, the generating force being a massive atomic boiler. Matt whistled softly. "We'll have to get the engineers down here right away." Isaac said, "Three basements, thirty floors. It'll take us a month to explore the building." Matt turned to Nesbit. "Go back to the ship, Hi. Tell Captain Bascom to send the chief engineer and the first assistant to put these atomic engines back in operation. The second assistant engineer is to start one of the trucks, load it with explosives and blow up all the bridges across Salt River except the highway bridge. "Tell Sawyer to take two more men and another truck and fortify the highway bridge. Dismount some of these machine guns if necessary, and set up a pill box at this end. String barbed wire across the bridge. Got it?" "Yes," said Nesbit. He turned to leave. "What should I do then?" "Get another truck and start hauling our equipment into the fort. Isaac and I are going to look over the upper floors." Nesbit nodded and strode toward the stairs. "Come along, Isaac," said Matt. "We've seen enough here." * * * * * During the next hour, Matt got a fair idea of the plan of the lower floors of the fort. They had entered through the freight entrance in the rear, the main doors fronting the highway, on the other side of which lay the small town of West Point. The lower levels were largely devoted to storage and offices. The fort, he realized, had been equipped to withstand a siege. There were tons of food and equipment. Above, they found forges, foundries, machine shops, laboratories and even hydroponic gardens. It was a world to itself; a world without any inhabitants. They were on the seventeenth floor, examining the modern, well-equipped guardhouse, when lights began to blink on. Matt said, "That was quick work." He found an inter communication televisor, hunted for the engine-room number and buzzed it experimentally. After a moment, the screen glowed and the square rough features of the chief engineer flashed in its depths. "Any trouble?" Matt asked. "Nary a bit. The engine had been shut down. That was all." "What about the elevators?" "Power's been cut in on all lines." "Good," said Matt. He snapped the televisor off, just as a dull boom sounded in the distance. "There goes one of the bridges," Isaac said nervously. Matt cut in the walkie-talkie strapped to his back. "Captain Bascom. Captain Bascom."