It's a shame that Lovecraft never wrote the story that he outlin'd in his letter to Kleiner of 27 Decr., 1719. It wou'd have been, had he actually penned it, the one story in his oeuvre in which a woman was the main character, although one feels that, as Lovecraft spells out ye plot to Kleiner, the story's narrator wou'd have been male. Lovecraft writes:
"The whole affair is one of vast singularity and mystery, and in my hands the tale would have become a horror story with a very different sort of climax. I should have had the lady display odd flashes of knowledge of the immemorial past, coupled with a certain mingled horror and contempt of old age. I should have had her shew, on the occasion of a trip through the Metropolitan Museum of Art, a curious fear when confronted with a particular inscription on an Egyptian stone. Then I should have had a friend of yours from Paris--let us call him M. Duval--meet her, and start back in fright--never quite daring to explain his fear, but afterward muttering to you that she queerly resembled a miniature which his great-great grandfather had worn in a locket, and which was connected with a peculiar family legend not pleasant to describe. And then I should have had you notice one morning before your mirror, that you were aging alarmingly and inexplicably--that your face, a few months before that of a youth, was now as that of a man of forty. You spoke to her of this, and her laugh sent a chill down your spine--and you noticed that she seemed younger than when you had first known her. Then your friend from Paris noticed the change in you and her--and would often become very thoughtful. He sent to his ancestral chateau in Vancluse for some documents--relating to some family financial arrangement, he told you, when one day you surprised him in the midst of the yellowed papers. And then you began to suspect that he was in the habit of following you and the lady--you even feared he would try to trace her to her home. One day the lady disappeared, and shortly afterward your friend returned to France."
This outline by Lovecraft continues for another full page. It may be found in the Arkham House volume, SELECTED LETTERS I, or in the Hippocampus Press volume (still available) H. P. LOVECRAFT: THE LETTERS TO REINHARDT KLEINER.