Agathemer opened the upper door of the secret stair, which unlike most doors, could be locked on either side, for my uncle always wanted to lock the doors he used, whichever way he passed through them. After we had passed this door Agathemer closed it behind us, and, as we stood in the pitch dark, locked it.

We groped our way down the dizzying turns of the steep stair, Agathemer going first and, at the bottom, whacking his knee-cap on the lower door. This he unlocked and I found myself in a dim-lit cellar which I had visited but twice before. Agathemer locked the stair-door behind us.

Now the minor tower, in which was the spiral stair, was built as a vent to carry up into the air, far above the roofs of the villa, any miasma, effluvium or exhalation from the drainage-water of the villa's baths, kitchen and latrines. On the subject of harmful vapours from drains my uncle was fanatical and to bear out his contentions he quoted from the works of many celebrated philosophers and physicians, including those of Galen.

Pursuant with his notions as to how to get rid of the exhalations from drainage and to make certain that no whiff of any such vapours ever found its way up any offset into his kitchen or any latrine or bathroom, he had built in this small high tower a shaft reaching its top and full six feet square all the way up. At its bottom it widened out into a chamber fully twelve feet square, carried down below the level of the cellar floor to form a cemented tank, vat, cistern or cesspool fully as deep as it was wide. The outfall from this trap was by a terra-cotta pipe of considerable size, its opening at such a point that the drain-water in the trap never reached higher than a foot or so below the level of the cellar floor. The various drainage-pipes from different parts of the villa were so led into this trap-room that their lower ends were always under water, so that no exhalations could ever pass up any of them.

To the bottom of the trap settled the solid matter and sediment from the drainage-water. The trap was cleaned by slaves so often that the ooze in it never rose high enough to escape down the outfall pipe and befoul the Bran Brook. For cleaning out the trap-room had an outer door, of heavy, solid oak, carefully locked, which when opened enabled the slaves entrusted with this task to dredge or bale or scoop out the filth and convey it off to be used as garden manure. There was also an inner door, as heavy and solid as the other, opening from the cellar, which enabled my uncle to inspect the trap at his convenience. This door Agathemer opened.

I peered in and, after my eyes became accustomed to the gloom, descried the opening of the outfall drain opposite me. It was large enough for lean men like me and Agathemer to crawl through, but certainly barely large enough. I could see, after some moments, the lower ends of the drain pipes, two dozen or more, dipping into the foul liquid which filled the cistern. It was very foul, for since my uncle's death the cleaning out of the trap had been neglected and the ooze came almost to the top of the water.

Agathemer hunted about the cellar, found some bits of stone about the size of apples, put them in the bag of food, tied up its neck again, and threw it into the trap, where it sank out of sight. After it he threw in the two keys.

Now was the moment for our plunge into the unknown. Agathemer's plan implied that we must crawl a full furlong through the outfall drain. We might be drowned, at any point of the crawl, by a rush of water from the bath-tank. We might suffocate in the foul vapours of the drain. But, plainly, Agathemer had pitched upon our only chance of escape, and we must escape that way and at once or not at all.

Agathemer threw the two copper cylinders, one after the other, neatly and deftly into the mouth of the outfall drain.

"Now," he said, "one of us must jump for that opening, and must cling to it, his arms inside, his body in the ooze of the trap. The other must stand on the narrow stone ledge inside this door, must contrive to slam the door behind him so that it will shut fast and stay shut, must then, in the pitch dark, jump for the shoulders of the other. If the drag of his weight pulls the other down, both of us will drown in this deep trap in the vile ooze. If the under man clings on, the upper must crawl over him into the drain, pass back to him one of the cylinders and then we shall be ready for our crawl down. Which goes first?"