The sun was gone now and the moon was coming out, touching pyramids and tumuli, earthworks and causeway with ghostly silver, deepening the effect of loneliness and far-off time.
While Ned was looking at these majestic remains he heard the sound of voices, and then the rattle of weapons.

He saw through the twilight the glitter of uniforms and of swords and sabers.

A company of Mexican soldiers, at least a hundred in number, had come into the ancient city and, no doubt, intended to camp there.

Being so absorbed in the strange ruins he had not noticed them sooner.
As the men were already scattering in search of firewood or other needs of the camp Ned saw that he was in great danger.

He hid behind a tumulus, half covered by the vegetation that had grown from its crevices.