To go back seemed the only way open. But the officer in the steel cap dived through a slit in the iron girders, and as he disappeared, beckoned. I followed down a well that dropped straight into the very bowels of the earth. It was very dark, and only crosspieces of wood offered a slippery footing. Into the darkness, with hands pressed against the well, and with feet groping for the log steps, we tobogganed down, down, down. We turned into a tunnel, and, by the slant of the ground, knew we were now mounting. There was a square of sunshine, and we walked out, and into a graveyard. It was like a dark change in a theatre. The last scene had been the ruins of a town, a gate like those of the Middle Ages, studded with bolts, reinforced with steel plates, guarded by men-at-arms in steel casques, and then the dark change into a graveyard, with grass and growing flowers, gravel walks, and hedges. The graves were old, the monuments and urns above them moss-covered, but one was quite new, and the cross above it said that it was the grave of a German aviator. As they passed it the French officers saluted. We entered a trench as straight as the letter Z. And at each twist and turn we were covered by an eye in a steel door. An attacking party advancing would have had as much room in which to dodge that eye as in a bath-tub. One man with his magazine rifle could have halted a dozen. And when in the newspapers you read that one man has captured twenty prisoners, he probably was looking at them through the peep-hole in one of those steel doors. We zigzagged into a cellar, and below the threshold of some one's front door. The trench led directly under it. The house into which the door had opened was destroyed; possibly those who once had entered by it also were destroyed, and it now swung in air with men crawling like rats below it, its half-doors banging and groaning; the wind, with ghostly fingers, opening them to no one, closing them on nothing. The trench wriggled through a garden, and we could see flung across the narrow strip of sky above us, the branch of an apple-tree, and with one shoulder brushed the severed roots of the same tree. Then the trench led outward, and we passed beneath railroad tracks, the ties reposing on air, and supported by, instead of supporting, the iron rails. We had been moving between garden walls, cellar walls; sometimes hidden by ruins, sometimes diving like moles into tunnels. We remained on no one level, or for any time continued in any one direction. It was entirely fantastic, entirely unreal. It was like visiting a new race of beings, who turn day into night; who, like bats, molochs, and wolves, hide in caves and shun the sunlight.