I was excited to begin Otto the Knight and Other Trans Mississippi Stories in part because of the regional focus. A few of these stories carry over characters from stories published in Knitters in the Sun. Michael B. and Carol W. Dougan's 1980 collection By the Cypress Swamp: The Arkansas Stories of Octave Thanet brings many of those stories together, although the title story "Otto the Knight" is not in that collection. Given the very light emphasis on the setting here, the omission of the story isn't completely surprising. McMichael also only mentions the story itself on page 125, indicating that it was chosen as the title for the collection solely based on the fact it was the first story.

The omission is interesting, given that Lum Shinault definitely lives on the Black River in "Whitsun Harp, Regulator" and because there is the connection to getting lost in the swamp. Marty Ann searching for Boo gets lost, just as Ma' Bowlin got lost in the earlier story. 

• Originally appeared in Century Magazine, XXXIV (May 1887), 111-125. Reprinted later that year in Knitters in the Sun.
• Characters: Polly Ann Shinault and Lum Shinault, Whitsun Harp, Bud Boas. Lum, Polly, and Boas are tenant farmers.
• Polly Ann is described as "Indian-like" multiple times: "She paddled as easily as an indian" (Thanet, p. 304); "Until she was fifteen she had lived the solitary life of the people and grown up in their Indian-like reticence. When she was fifteen, her mother died and her father took her to Clover Bend" (Thanet, p. 317). "They spoke together in a low tone, but Polly Ann had the ears of an indian" (Thanet, p. 346).
• Polly Ann and Whitsun Harp were childhood friends and they carry the same bearing--this means that Harp also grew up in the Sunk Lands.
• The cypress swamp is again like a character; the magical nature of it pops up on page 308. After describing the swamp as a hideout for war criminals and later for escaped prisoners, Thanet mentions that "Plenty of grim traditions hung, heavy as its own miasma, over the cypress swamp" (Thanet, p. 308). Polly Ann is from "the 'Sunk Lands,' that mysterious region created by the great Lisbon earthquake,--an island in the swamps, half the year cutoff from the world, forgotten except by a few traders" (Thanet, p. 317). 
• McMichael calls "Whitsun Harp" the "best story in the collection" (p. 107) and indicated that even Howells "judged the author had resorted toan unrealistic ending to save the hero from sin. Howells liked to see wickedness punished" (p. 107). but he found the ending trite . McMichael includes,in full, the response letter French wrote to his criticism (see pp. 108-109).
• Thanet to Howells: "Then you most justly remark that a fairy providence is unworthy of fiction and find the whole proceeding wrong and unnatural" (McMichael, p. 108). She continues with "I quite agree with you. Only, dear Mr. Howells, I didn't do it" ​(p. 108). See below.
• McMichael notes that Howell "was apologetic. He had indeed misread the story and promised to retract his comments. And he asked permission to quote from herletterin his 'Editor's Study'" (p. 109). Her response to his request is printed on pages 109-110, and is interesting due to her focus on realism. See below for a partial response (McMichael, p. 110)

Basic Plot Summary: 

Part I: Polly Ann Shinault, wife of Lum, is out fixing the Clover Bend ferry-boat when she sees Whitsun Harp in the boat with her neighbor Boas. Harp has come by because he's heard Lum and Polly are missing a mule, and Polly acknowledges that, saying that Lum is off looking for it, but they assume it has been stolen. He proceeds to tell her his story of becoming a regulator, and how it seems like a calling from God. 

It's pretty clear Harp was sweet on Polly but Lum beat him to her. Harp mentions that as kids they played together and he told her everything then, which is why he felt the need to personally tell her why he had become a regulator.When he leaves, Boas tells Polly that Harp already warned Lum to shape up and to stop partying. He emphasizes the importance of Lum doing so by telling her different stories of Harp "giving a lickin'" to various people.

Lum comes home for supper and when Polly tells him Harp finds him "trifflin'" Lum indicates Harp had better mind his own business. We learn that Lum helps his wife with household chores, having helped his mother because his father was 'triflin.'" We also learn that "he had married Polly Ann out of compassion" (Thanet, p. 316) when her father died. He reasoned that "Nary un waiti' on 'er neether, 'less hit ar' Whitsun Harp. Ef he don' marry her, I reckon Ihed orter. 'Tain't no mo'n neighborly.' //Whitsun making no sign, he carried out his intention" (Thanet, p. 316).

In a conversation with Boas, Lum reveals the truth about his interactions with Savannah Lady. They are merely trying to make the man she loves jealous, and Lum thinks there's no harm in it. The trick works, and Morrow proposes to Savannah. Unfortunately, Lum, Whitsun, Polly, and Savannah all converge in the dry bottoms of the swamp and Harp mistakes Lum helping Savannah by giving her whiskey when she is ill to be some romantic tryst. He breaks of a switch and beats Lum. Polly sees it all and chides Lum for not standing up for himself, but she assures him she'll cook him a good dinner.

Lum is ashamed and cries because he thinks Polly doesn't love him, and he's sure this was the final straw. 

Part II:  Lum doesn't come home for dinner, despite Polly waiting. She finds a note that indicates he won't be back (Thanet, p. 328). He has taken the gun and plans to kill Whitsun Harp. "He had been beaten before his wife, his wife who valued strength and bravery beyond everything. And Whitsun, whom she praised because he was so strong and brave had beaten him" (Thanet, p. 328). He knows this is a high priority for Polly as her father, Old Man Gooden, shot a man for spitting in his face. According to Polly, "Paw hed ter shoot him" (Thanet, p. 329).

Lum assumes Polly pines after Harp, and he decides that if Harp kills him, Polly won't take up with him. On the other hand, if he kills Harp, Polly will never forgive him, either. So, his plan is to "go off on the cotton-boat afore sundown. All through this wide worl' I'll wander, my lone" (Thanet, p.329). 

Lum (short for Columbus) crosses paths with Boas,who is dying. Boas tells Lum he's come out to warn Harp that some other men are coming to kill him. Boas killed another man a few years back, and ever since he's been haunted by it. He fears going to hell, and he hopes that by warning Harp, God will give him mercy. Unfortunately, he's too weak to go all the way across the swamp and he begs Lum to do it for him. Lum does, but he tells Harp that as soon as Boas dies, he will kill Harp. Harp, upon hearing the truth about Savannah, swears he'll make it up to Lum and Polly, but Lum says there's no way he can.

It takes three weeks for Boas to die and Lum acts weird, taking to the woods mostly. Polly worries about him and follows him, but she's not sure what to do and just fears he's gone mad. When Boas dies, Lum joins Harp at the grave and tells him he's still going to kill him and where to meet after the funeral. Harp asks Lum to meet him at the plantation store first, and he does. Harp makes things right by admitting to being wrong and apologizes.  He and Lum shake hands, and Lum decides to go squirrel hunting.

Meanwhile, Polly notices Lum's boat is gone and she follows him to Clover Bend (using Boas' boat). She hears a single shot and runs towards it, finding Harp dead on the ground, a smile on his face. Lum is nearby, but he tells her the story of how Harp made things right and that it wasn't he who shot him.  He tells Polly he'll leave her to her goodbyes, and she realizes he thinks she loves Harp.  It turns out she never loved anyone but Lum, and the story ends with them embracing, Harp's dead, smiling body still on the ground.