In a shady glade not far from the New England village of New London, two men, one a physician, in late life named Doctor Allen, the other a writer in mid-life named Hale Morgan, encountered an invisible opening then, when they passed through, projected them into that Other Place, which was so unique that neither of them ever managed to fully comprehend it.
But meanwhile two other men also blundered into that Other Place, got another view too and although those two died, leaving the secret with Hale and Doc Allen, by then the police were interested so Doc and Hale had to do their utmost to conceal their secret.
They succeeded in concealing it, but they also succeeded in never entering it again either, and so the mystery was never satisfactorily resolved.