A mysterious stranger can be good...or evil

"Thurlo's Christmas Story," by ? Bangs, makes a good contrast with the powerful, feminist Yellow Wallpaper, this one about a man going mad, primarily from the stress of his work (he's a writer). Thurlo has to write an xmas story by an October 5th deadline for his magazine editor. He's unable to do so; his words seem to break apart on the page. He writes a long "letter" (i.e., the story we are reading) to his editor explaining his failure: he's been going mad, seeing his "double" as a version of all the evil thoughts within in, an evil twin. Oddly, as he is trying to write, an "elderly" (50 years old, yikes!) man rings his bell - introduces himself as a great fan. They talk, the mysterious stranger leaves a manuscript of a story, says Thurlo can submit it; it's a masterpiece. After trepidation, Thurlo sends it in; the editor responds that he received 24 blank pages, and Thurlo writes the story we're reading as an explanation. Last paragraphs: editor responds that the explanation itself is the best thing Thurlo has ever written. A touch of postmodernist whimsy here, well before its time - as on another level of cognition this story by the obscure Bangs (an editor himself his day, according to Straub's notes in the Library of America "Fantastic American Tales," is no doubt the best story Bangs ever wrote. The mysterious stranger is another kind of trope in "fantastic" fiction, sometimes benevolent and sometimes not. This story has both. Next story in the anthology is futurist story, written ca 1890 set in 1920! He didn't get much right; I'm still reading it and trying to make sense of it.