To most minds mystery is more fascinating than science. But when science itself leads straight up to the borders of mystery and there comes to a dead stop, saying, “At present I can no longer see my way,” the force of the charm is redoubled.

One confidential evening, not three months ago, Lionel Wallace told me this story of the Door in the Wall. And at the time I thought that so far as he was concerned it was a true story. He told it me with such a direct simplicity of conviction that I could not do otherwise than…