The Wolves of God by Algernon Blackwood

The incident -- story it never was, perhaps -- began tamely, almost meanly; it ended upon a note of strange, unearthly wonder that has haunted him ever since. In Headley's memory, at any rate, it stands out as the loveliest, the most amazing thing he ever witnessed. Other emotions, too, contributed to the vividness of the picture. That he had felt jealousy towards his old pal, Arthur Deane, shocked him in the first place; it seemed impossible until it actually happened. But that the jealousy was proved afterwards to have been without a cause shocked him still more. He felt ashamed and miserable.

For him, the actual incident began when he received a note from Mrs. Blondin asking him to the Priory for a week-end, or for longer, if he could manage it.