From the topmost summit of that range of pointed hills which held the caves and the cave-mouth fires of his people, Grom stared northward with keen curiosity. To east and south and west he had explored, ever seeking to enlarge the knowledge and strengthen the security of his tribe. But to northward of the pointed hills lay league on league of profound jungle--grotesque and enormous growths knitted together impenetrably by a tangle of gigantic, flame-flowered lianas. And in those rank, green glooms, as Grom had reason to believe, there lurked such monsters as even he, with all his resources of fire and novel weapons, had so far shrunk from challenging. But beyond the expanse of jungle stretched another line of hills, their summits not saw-toothed like his own, but low and gently rounded, and of a smoky purple against the pure turquoise sky. These hills Grom was thirsting to explore. They might contain caves more roomy than those of his own hills--spacious and suitable to give shelter to his tribe, which was now finding itself somewhat cramped. Moreover, it had always seemed to Grom that there might be a mystery behind those hills, and to his restless imagination a mystery was always like a stinging goad. In all this neighborhood the crust of earth was thin as plainly appeared from the fringe of wavering volcanic flames which, during all the five years since the coming of the tribe, had been dancing from the lip of the narrow fissure across the mouth of their valley. Night and day, now high and vehement, now low and faint, they had danced there, guarding the valley entrance--until just one moon ago. Then had come an earthquake, shaking the hearts of all the tribe to water. The dancing flames had died. The fissure had closed up, and its place had been taken by a pool of boiling pitch. And one of the caves had fallen in, burying several members of the tribe, who had been too stupefied with panic to flee into the open at the first alarm. For some days after this catastrophe the tribe had camped in the open, huddled about their great fires. Then, but with deep misgivings, they had all crowded back into the remaining caves. But now there was not room enough, and Bawr, the wise Chief, had taken frequent counsel upon the matter with Grom, whom, loving him greatly he called sometimes his Right Hand and sometimes the Eye of the People. At last, it had been settled that Grom should lead a party through the jungle land to those other hills, to spy out the prospect. And Grom, like the foresighted leader that he was, had spent many hours on the mountain-top, planning his route and studying the luxuriant surface of the jungle outstretched below him, before plunging into its mysterious depths.