Louis had published a brief monograph in a prestigious xeno-archaeology journal, speculating—not entirely seriously—that the lack of Klikiss cadavers might indicate that the lost race engaged in ritual cannibalism, devouring their dead and leaving no remnants. As evidence, he pointed to the fact that there were no cemeteries, tombs, or any indications whatsoever of Klikiss burial practices. Louis’s conjecture had met with skepticism and a brief flurry of debate, but because of his stature in their field, no one dared call Louis a crackpot.

As they explored, the fused stone corridors widened, tending toward what seemed to be a nexus in the cliff city. DD tromped ahead with the light, and they followed into another chamber. The air in this room vibrated with a strange humming silence, as if some odd quality of the stone walls themselves absorbed echoes.

As in most of the Klikiss chambers, every smooth surface here was covered with designs, writing, hieroglyphics, and mathematical symbols—as if the insectoid race felt compelled to record thoughts and historical events for all to see. Oddly, though they were clearly a star-traveling race with colonies on many planets, the Klikiss had also never drawn any images of spacecraft or other vehicles on their walls.

Encased machinery crouched in one corner of the room, casting razor-edged shadows. As DD shone his glowpanel around the chamber, Margaret saw that a major section of the primary wall was completely blank, a trapezoidal sheet of stone like a virgin canvas, framed by a dense perimeter of symbols. The blank space was striking in contrast to the sheer density of designs and pictographs on every other clear surface of the wall.

“Well, it looks like the Klikiss weren’t finished here,” Louis said. “But why avoid that particular section? Some quality of the stone, perhaps?”

Margaret shook her head. “No, old man. Look, it’s a perfect trapezoid. This patch was left intentionally blank, as if they needed it clean and flat for something. We’ve seen this before in some of the other ruins.”

“Yes, now I remember. But we never figured it out, dear.”

Arcas hunkered down and contemplated the flat trapezoid, which was three meters across at its base. “It looks to me like a broad window … or a door.”

Margaret could not argue with his impression, because she’d had the same eerie feeling. “But where would it go? There’s nothing but stone behind it.” She went forward to study the inscribed symbols bordering the blank space, compelled and curious. The few other “stone windows” they had previously discovered had been surrounded by rubble or damaged in some way. This one was intact.

But its purpose was still unclear.