There was no mistaking it. This was, in very deed, the portal through which Throckmartin had seen pass that gloriously dreadful apparition he called the Dweller. At its base was the curious, seemingly polished cup-like depression within which, my lost friend had told me, the opening door swung.

What was that portal⁠—more enigmatic than was ever sphinx? And what lay beyond it? What did that smooth stone, whose wan deadness whispered of ages-old corridors of time opening out into alien, unimaginable vistas, hide? It had cost the world of science Throckmartin’s great brain⁠—as it had cost Throckmartin those he loved. It had drawn me to it in search of Throckmartin⁠—and its shadow had fallen upon the soul of Olaf the Norseman; and upon what thousands upon thousands more I wondered, since the brains that had conceived it had vanished with their secret knowledge?

What lay beyond it?