The underground room in which he found himself was smaller than the space covered by the cottage. The walls were of large rough stones, showing evidence of dampness. Along these walls was piled litter of a varied nature—old barrels, boxes, empty food tins and the broken remains of furniture. Against the front wall, at a point almost under the entrance door, stood an old, dilapidated sideboard. It attracted Forrester’s attention because he could not conceive how such a large object had been brought into the cellar through the small trap. It was the only thing in the cellar that could be readily moved, and Forrester had an inspiration to look behind it. At the first effort the sideboard swung out from the wall on smooth-running casters that strangely had apparently not been affected by the dampness of the cellar. Moving the sideboard disclosed a small, rough-board door in the wall. This Forrester opened and flashed his light into the space beyond. It seemed to be a narrow passage, the floor a little below the level of the cellar. Forrester dropped into the passage and started along it, throwing his light about him and studying its formation. The floor was sandy, the walls of solid rock, and the roof appeared to have been formed by a multitude of interlacing tree and plant roots. The average width of the passage was about five feet and its height somewhere between ten and twelve. Forrester’s trained eye saw instantly that it was the work of Nature, not of man. At some remote period a cleft had been riven in the solid rock and the intertwined roots above prevented the caving in of the surface soil. A momentary sparkle on the ceiling caught Forrester’s eye. He then discovered that electric lights were hung from the roof at regular intervals. They were beyond his reach, and as no connection or switch along the walls had been discovered, Forrester concluded that the lights could be operated only from some point inside the cottage. Presently Forrester came to an indentation in the wall on his right, forming a sort of shelf. On this rested two bright steel cylinders about the size of the small fire extinguisher he carried in his car. To one of the cylinders was attached a five-foot length of a slender rubber tubing which connected it with one of the rubber death masks he knew only too well. Here at last was evidence beyond dispute. Forrester did not meddle with the cylinders. The slightest mistake made by one unaccustomed to them might release the deadly gas he had reason to believe they contained. In that confined space its action would be swift and sure. Continuing along the passage Forrester finally came to the end. At this point it widened out slightly into a small chamber. At one side a ladder led up into a mass of tangled tree roots that hung in fantastic shapes, which gave Forrester an uncomfortable feeling that he had stumbled into a veritable den of snakes. Forcing back this feeling of revulsion he climbed the ladder.