The engineer was already bathed in a heavy sweat. The intense heat, well above a hundred degrees, added to the humidity, almost stifled him. His bound arms pained almost beyond endurance. Unable to balance himself, he slipped and staggered.

“Beatrice!” he called chokingly. “Try to make them understand I want my hands freed. It's bad enough trying to clamber up this infernal road, anyhow, without having to go at it all trussed up this way.”

She, needing no second appeal, raised her free arms, pointed to her wrists and then at his, and made a gesture as of cutting. But the elder boatman of Stern's canoe--seemingly a person of some authority--only shook his head and urged the prisoners upward, ever upward toward the great and growing light.

Now they had reached the top of the ascent.

On either hand, vanishing in shadows and mist, heavy and high walls extended, all built of black, cut stone surmounted by cressets.

Through a gateway the throng passed, and the prisoners with them--a gateway built of two massive monoliths of dressed stone, octagonal and highly polished, with a huge, straight plinth that Stern estimated at a glance never could have weighed less than ten tons.

“Ironwork, heavy stonework, weaving, fisheries--a good beginning here to work on,” thought the engineer. But there was little time for analysis. For now already they were passing through a complex series of inner gateways, passages, detours and labyrinthic defenses which--all well lighted from above by fire-baskets--spoke only too plainly the character of the enclosure within.

“A walled town, heavily fortified,” Stern realized as he and Beatrice were thrust forward through the last gate. “Evidently these people are living here in constant fear of attack by formidable foes. I'll wager there's been some terrible fighting in these narrow ways--and there may be some more, too, before we're through with it. God, what a place! Makes me think of the machicoulis and pasterns at old Carcassonne. So far as this is concerned, we're back again in the Dark Ages--dark, dark as Erebus!”

Then, all at once, out they issued into so strange a scene that, involuntarily, the two captives stopped short, staring about them with wide eyes.

Stretching away before them till the fog swallowed it--a fog now glowing with light from some source still mist-hidden--an open plaza stretched. This plaza was all surrounded, so far as they could see, with singular huts, built of dressed stone, circular for the most part, and with conical roofs like monster beehives. Windows there were none, but each hut had an open door facing the source of the strange, blue-green light.