There was silence in the cave, but, outside, the world was not so still. The night was not always one of silence in the cave man's time. The hours of darkness were those when the creature which walked upon two legs was no longer gliding through the forest with ready club or spear, and when those creatures which used four legs instead of two, especially the defenseless, felt more at ease than in the daytime. The grass-eating animals emerged from the forest into the plateaus and upon the low plains along the river side and the flesh-eaters began again their hunting. It was a time of wild life, and of wild death, for out of the abundance much was taken; there were nightly tragedies, and the beasts of prey were as glutted as the urus or the elk which fed on the sweet grasses. It was but a matter of difference in diet and in the manner of doing away with one life which must be sacrificed to support another. There was liveliness at night with the queer thing, man, out of the way, and brutes and beasts of many sorts, taking their chances together, were happier with him absent. They could not understand him, and liked him not, though the great-clawed and sharp-toothed ones had a vast desire to eat him. He was a disturbing element in the community of the plain and forest. And, while all this play of life and death went on outside, the three people, the man, woman and child, in the cave slept as soundly as sleep the drunken or the just. They were full-fed and warm and safe. No beast of a size greater than that of a lank wolf or sinewy wildcat could enter the cave through the narrow entrance between the heaped-up rocks, and of these, as of any other dangerous beast, there was none which would face what barred even the narrow passage, for it was fire. Just at the entrance the all-night fire of knots and hardest wood smoked, flamed and smoldered and flickered, and then flamed again, and held the passageway securely. No animal that ever lived, save man, has ever dared the touch of fire. It was the cave man's guardian. CHAPTER IV. AB AND OAK.