So we glanced back simultaneously, it would appear, though no doubt the incipient motion of one prompted the imitation of the other. As we did so we flashed both torches full strength at the momentarily thinned mist, either from sheer primitive anxiety to see all we could, or in a less primitive but equally unconscious effort to dazzle the entity before we dimmed our light and dodged among the penguins of the labyrinth centre ahead. Unhappy act! Not Orpheus himself, or Lot’s wife, paid much more dearly for a backward glance. And again came that shocking, wide-ranged piping – ‘Tekeli-li! Tekeli-li!’

I might as well be frank – even if I cannot bear to be quite direct – in stating what we saw, though at the time we felt that it was not to be admitted even to each other. The words reaching the reader can never even suggest the awfulness of the sight itself. It crippled our consciousness so completely that I wonder we had the residual sense to dim our torches as planned, and to strike the right tunnel toward the dead city. Instinct alone must have carried us through – perhaps better than reason could have done; though if that was what saved us, we paid a high price. Of reason we certainly had little enough left.

Danforth was totally unstrung, and the first thing I remember of the rest of the journey was hearing him light-headedly chant an hysterical formula in which I alone of mankind could have found anything but insane irrelevance. It reverberated in falsetto echoes among the squawks of the penguins, reverberated through the vaultings ahead, and – thank God – through the now empty vaultings behind. He could not have begun it at once – else we would not have been alive and blindly racing. I shudder to think of what a shade of difference in his nervous reactions might have brought.

‘South Station Under – Washington Under – Park Street Under – Kendall – Central – Harvard – ’ The poor fellow was chanting the familiar stations of the Boston-Cambridge tunnel that burrowed through our peaceful native soil thousands of miles away in New England, yet to me the ritual had neither irrelevance nor home feeling. It had only horror, because I knew unerringly the monstrous, nefandous analogy that had suggested it. We had expected, upon looking back, to see a terrible and incredible moving entity if the mists were thin enough; but of that entity we had formed a clear idea. What we did see – for the mists were indeed all too malignly thinned – was something altogether different, and immeasurably more hideous and detestable. It was the utter, objective embodiment of the fantastic novelist’s ‘thing that should not be’; and its nearest comprehensible analogue is a vast, onrushing subway train as one sees it from a station platform – the great black front looming colossally out of infinite subterranean distance, constellated with strangely coloured lights and filling the prodigious burrow as a piston fills a cylinder.