What caused Tristan to pause in the night gloom of the corridor leading to the Pontifical Chapel he did not know. He seemed as under a strange spell. At a distance from him of some five feet, in the decorated wall, there was a dark panel some two feet in height and of corresponding breadth, looking obliquely towards the Pontifical Chapel. The panel contained a small round opening, a spy-hole which communicated with a secret chamber in the thickness of the wall.
A slight rustling noise came from behind the masonry. Tristan heard it quite distinctly. It suggested the passing of naked feet over marble.
Suddenly, noiselessly the panel parted.
A sudden gleam of white, blinding light shot into the chapel like a spear of silver.
Tristan paused with a start, looking swiftly and inquiringly at the black slit in the wall and as he did so the spear of light shifted a little in its passing.
A face, white with the pallor of death, ghastly and hideous as a corpse that has retained upon its set features the agony of dying, peered out from blackness into blackness.
A tremor shook Tristan's frame from head to toe. He could not have cried out, had he wished to. He felt as one grazed by a lightning bolt. Then, in a flash that made his heart and soul shudder within him, he knew.
He had seen looking at him a face—the clean shaven face of a man. But it was not human. It bore the terrible stigmata of the unquenchable fire; an abominable vision of the lust that cannot be satiated, the utter, unconquerable, fiendish malevolence of Hell. A harsh, raven-like croak broke the stillness, and at the sound of that cry the terrible face vanished with the swiftness of a trick. Instead, a long arm, clothed in a black sleeve, stole through the opening. A flash, keen as that of the lightning, cut the air and a dagger struck the mosaic floor at Tristan's feet with such force that its point snapped after shattering the stone, drawing fire from the impact.
Bounding back, Tristan uttered a shrill cry of terror, but when he looked in the direction of the panel only dim dun dusk met his eyes.
Rushing frantically from the corridor he now called with all his might. His outcries brought the guards to the scene. Briefly, incoherently, almost mad with terror, he told his tale. They listened with an air of amazement in which surprise held no small share. Then they accompanied him back to the chapel.