“Letter to Weird Tales”, March 1924 (PDF). Lovecraft tells editor Baird of his new-found Providence pal Eddy, and their coming hike out in search of the mysterious Dark Swamp. Eddy had lingered in a corner-store in Chepachet and by chance overheard local lore about a vast ‘Dark Swamp’ west of Durfee Hill, which hunters said was always dark even at noon. And so…

Eddy began writing a story about it — provisionally entitled “Black Noon” — on the trolley ride home. Now we are both to see it … we are both to go into that swamp … and perhaps to come out of it. Probably the thing’ll turn out to be a clump of ill-nourished bushes, a few rain-puddles, and a couple of sparrows — but until our disillusion we are at liberty to think of the place as the immemorial lair of nightmare and unknown evil ruled by that subterraneous horror that sometimes cranes its neck out of the deepest potholes… It.

“Black Noon” was later partly written — although if from the original 1923 trolley-car draft/notes is unknown — by Eddy in 1967. He had earlier recalled something of the real Dark Swamp journey in his 1966 memoir (see Lovecraft Remembered). Eddy died before the “Black Noon” tale could be finished. It was however substantial enough to be published in…

* The Eddy collection Exit Into Eternity: Tales of the Bizarre and Supernatural, 1973, and 2000 reprint.

* The Robert M. Price edited miscellaneous anthology Acolytes of Cthulhu, 2001. Rights meant it had to be omitted from the later 2014 Titan reprint edition.

So far as I can discover, these are the only places it has been published. Derleth is said to have considered ‘finishing’ it as a tale, but didn’t.