Up these openings, as captive and captors passed them, came strange sounds, boomings and clangings, as of a mighty forge, and at times a lurid glow would flash up for an instant, then die away again.

Past all these openings the priest went, pausing at length before the open doorway of a rock chamber.

“Enter,” he commanded, and, realising the futility of resistance, the scientist obeyed.

The light of the priest’s stone illumined every corner of the chamber. A rough rectangle it was in shape, about twenty feet by twelve. Across the floor, parallel with, and about a couple of feet from, the doorway, ran a strange crack, not more than three inches in width at its widest part.

Over this Mervyn stepped, then turned and faced his captors.

“I will give thee time to decide,” Nordhu said, “whether ye will do my bidding or be delivered to the sacred beast of Ramouni. See, here is food”—flinging a couple of mushroom-like fungi towards his prisoner—“eat, and think well over your answer. Thy fate is in thine own hands.”

“Stand back against the further wall,” he added, a moment later. Without a word Mervyn obeyed. As he did so Nordhu stamped with his foot upon the floor of the passage. Instantly, from the crack in the floor leapt a dazzling sheet of flame, forming an impenetrable barrier between the scientist and the doorway. Almost to the roof the flaming wall towered, darting and flashing in innumerable little tongues.

The heat from the barrier was terrible; its glare seemed to shrivel Mervyn’s eyes, and his ears throbbed with the roaring of the flames.

The fungi lay untasted at his side, and he sat with his head buried in his hands, the personification of despair.

His fate was in his own hands, so the priest had said; his own it was to decide whether he should earn freedom or a terrible death.