With the lighted candle in his hand, he came towards the flight of steps. At the top of this stone stairway, he paused for a moment almost daunted. It seemed to have no end. The light of the candle became swallowed up in the darkness before revealing the last step. There were over a hundred of these steps leading to a passage, or rather a tunnel, which ended by opening into a corridor. The tunnel struck the corridor at right angles, and Lavenne, holding his light to the walls, looked in vain for an indication as to whether he should turn to the right or the left. Failing to find any, he turned to the right.

He had gone only a few yards when an opening in the corridor wall gave him a glimpse of something more daunting than the darkness. It was a skull resting on a heap of bones. The skull, from which the lower jaw was missing, was yet not wholly without speech. It told Lavenne at once where he was.

Pursuing his way and casting the light of the candle into several more of these lidless sarcophagi, he reached a large open space, where over the piles of bones heaped against the walls, the candle-light revealed a Latin inscription cut into the stone.

From this open space to the right, to left, in front and behind of the man who had just entered it, the candle-light showed four corridors each leading to darkness.

Lavenne had left the laboratory of Count Camus only to find himself entangled in the Catacombs of Paris.

Camus’ house seemed built in conformity with his mind, secure, secret, containing many things unrevealable to the light of day, and based on a maze of dark passages offering a means of escape to the mind that knew them and bewilderment and despair to the mind that did not.

Lavenne knew something of the catacombs, but not much. They lay outside his province.

The Catacombs of Paris are to-day just as they were in the time of the fifteenth Louis, with this difference: they are more fully occupied, since they contain the bones of many of the victims of the Terror. This vast system of tunnelling which extends from the heart of Paris to the plain of Mont Souris is in reality a city where rock takes the place of houses, galleries the place of streets, dead men the place of citizens, and eternal darkness the place of day and night.

It has been closed now for some years on account of the danger to explorers arising from the huge army of rats that have made it their camping-ground. Some years ago a man was attacked and eaten by rats in one of the galleries.