“The Thing in the Moonlight” is based on a letter that Lovecraft wrote to Donald Wandrei on 24 November 1927. The story surrounding Lovecraft’s description of his dream was written by J. Chapman Miske and published in the January 1941 issue of Bizarre.

Letter to Donald Wandrei		“The Thing in the Moonlight”
My dreams occasionally approach’d the phantastical in character, tho’ falling somewhat short of coherence. One scene is especially stamp’d upon my recollection—that of a dank, fœtid, reed-choak’d marsh under a grey autumn sky, with a rugged cliff of lichen-crusted stone rising to the north. Impell’d by some obscure quest, I ascended a rift or cleft in this beetling precipice, noting as I did so the black mouths of many fearsome burrows extending from both walls into the depths of the stony plateau.		Morgan is not a literary man; in fact he cannot speak English with any degree of coherency. That is what makes me wonder about the words he wrote, though others have laughed. He was alone the evening it happened. Suddenly an unconquerable urge to write came over him, and taking pen in hand he wrote the following: My name is Howard Phillips. I live at 66 College Street, in Providence, Rhode Island. On November 24, 1927—for I know not even what the year may be now—, I fell asleep and dreamed, since when I have been unable to awaken. My dream began in a dank, reed-choked marsh that lay under a gray autumn sky, with a rugged cliff of lichen-crusted stone rising to the north. Impelled by some obscure quest, I ascended a rift or cleft in this beetling precipice, noting as I did so the black mouths of many fearsome burrows extending from both walls into the depths of the stony plateau.
At several points the passage was roof’d over by the choaking of the upper parts of the narrow fissure; these places being exceedingly dark, & forbidding the perception of such burrows as may have existed there. In one such dark space I felt conscious of a singular accession of fright, as if some subtile & bodiless emanation from the abyss were ingulphing my spirit; but the blackness was too great for me to perceive the source of my alarm.		At several points the passage was roofed over by the choking of the upper parts of the narrow fissure; these places being exceeding dark, and forbidding the perception of such burrows as may have existed there. In one such dark space I felt conscious of a singular accession of fright, as if some subtle and bodiless emanation from the abyss were engulfing my spirit; but the blackness was too great for me to perceive the source of my alarm.
At length I emerg’d upon a table-land of moss-grown rock & scanty soil, lit up by a faint moonlight which had replac’d the expiring orb of day. Casting my eyes about, I beheld no living object; but was sensible of a very peculiar stirring far below me, amongst the whispering rushes of the pestilential swamp I had lately quitted.		At length I emerged upon a tableland of moss-grown rock and scanty soil, lit by a faint moonlight which had replaced the expiring orb of day. Casting my eyes about, I beheld no living object; but was sensible of a very peculiar stirring far below me, amongst the whispering rushes of the pestilential swamp I had lately quitted.
After walking for some distance, I encounter’d the rusty tracks of a street-railway, & the worm-eaten poles which still held the limp & sagging trolley wire. Following this line, I soon came upon a yellow, vestibuled car numbered 1852—of a plain, double-trucked type common from 1900 to 1910. It was untenanted, but evidently ready to start; the trolley being on the wire & the air-brake pump now and then throbbing beneath the floor. I boarded it & looked vainly about for the light switch—noting as I did so the absence of controller handle which implied the brief absence of the motorman. Then I sat down in one of the cross seats toward the middle, awaiting the arrival of the crew & the starting of the vehicle. Presently I heard a swishing in the sparce grass toward the left, & saw the dark forms of two men looming up in the moonlight. They had the regulation caps of a railway company, & I could not doubt but that they were the conductor & motorman. Then one of them sniffed with singular sharpness, & raised his face to howl to the moon. The other dropped on all fours to run toward the car.		After walking for some distance, I encountered the rusty tracks of a street railway, and the worm-eaten poles which still held the limp and sagging trolley wire. Following this line, I soon came upon a yellow, vestibuled car numbered 1852—of a plain, double-trucked type common from 1900 to 1910. It was untenanted, but evidently ready to start; the trolley being on the wire and the air-brake now and then throbbing beneath the floor. I boarded it and looked vainly about for the light switch—noting as I did so the absence of the controller handle, which thus implied the brief absence of the motorman. Then I sat down in one of the cross seats of the vehicle. Presently I heard a swishing in the sparse grass toward the left, and saw the dark forms of two men looming up in the moonlight. They had the regulation caps of a railway company, and I could not doubt but that they were conductor and motorman. Then one of them sniffed with singular sharpness, and raised his face to howl to the moon. The other dropped on all fours to run toward the car.
I leaped up at once & raced madly out of that car & away across endless leagues of plateau till exhaustion waked me—doing this not because the conductor had dropped on all fours, but because the face of the motorman was a mere white cone tapering to one blood-red tentacle. . . .		I leaped up at once and raced madly out of that car and across endless leagues of plateau till exhaustion forced me to stop—doing this not because the conductor had dropped on all fours, but because the face of the motorman was a mere white cone tapering to one blood-red-tentacle. . . .
		I was aware that I only dreamed, but the very awareness was not pleasant.
		Since that fearful night, I have prayed only for awakening—it has not come!
		Instead I have found myself an inhabitant of this terrible dream-world! That first night gave way to dawn, and I wandered aimlessly over the lonely swamp-lands. When night came, I still wandered, hoping for awakening. But suddenly I parted the weeds and saw before me the ancient railway car—and to one side a cone-faced thing lifted its head and in the streaming moonlight howled strangely!
		It has been the same each day. Night takes me always to that place of horror. I have tried not moving, with the coming of nightfall, but I must walk in my slumber, for always I awaken with the thing of dread howling before me in the pale moonlight, and I turn and flee madly.
		God! when will I awaken?
		That is what Morgan wrote. I would go to 66 College Street in Providence, but I fear for what I might find there.