"There's an inscription of some sort," said Kelburn loftily. "This thing was left for a purpose. Somewhere there must be operating instructions." "From here, it looks like a complex wave-form," a voice crinkled in their radio--Taphetta from the spaceship. "All we have to do is to find the right base in the electromagnetic spectrum and duplicate it on a beam broadcast and the door should open. You're too close to see it as clearly as I can." * * * * * Perhaps they were too close to the big ancestor, decided Halden moodily as they went back. It had overshadowed much of their thinking, and who really knew what the ancestor was like and what had motivated him? But the Ribboneer was right about the signal, though it took several days to locate it. And then the huge door swung open and air whistled out. Inside was another disappointment, a bare hall with a ramp leading upward, closed off at the ceiling. They could have forced through, but they had no desire to risk using a torch to penetrate the barrier--in view of the number of precautions they'd already encountered, it was logical to assume that there were more waiting for them. It was Emmer who found the solution. "In appearance, it resembles a spaceship. Let's assume it is, minus engines. It was never intended to fly. Listen. "There's no air, so you can't hear," said Emmer impatiently. "But you could if there were air. Put your hands against the wall." A distinct vibration ran through the whole structure. It hadn't been there before the door opened. Some mechanism had been triggered. The rumbling went on, came to a stop, and began again. Was it some kind of communication? Hastily rigged machines were hauled inside the chamber to generate an air supply so that sounds would be produced for the recorders. Translating equipment was set up and focused and, after some experimentation with signals, the door was slowly closed. No one remained inside; there was no guarantee that it would be as easy to get out as it had been to get in. They waited a day and a half while the sounds were being recorded. The delay seemed endless. The happiest of the crew was Kelburn. Biologically the highest human on the expedition, he was stimulated. He wandered aimlessly and smiled affably, patting Meredith, when he came to her, in the friendliest fashion. Startled, she smiled back and looked around wanly. Halden was behind her. If I had not been there, thought Halden--and thereafter made it a point to be there. * * * * * Meredith was excited, but not precisely happy. The work was out of her hands until the translating equipment was retrieved. As the second highest biological type, she, too, was affected, until she pointedly went to her room and locked it from the inside. Halden kept himself awake with anti-fatigue pills, in part because Meredith could change her mind about Kelburn, and because of that locked door.