Almost a year has passed since the last chapter. Ab Snopes, a local poor white who Colonel Sartoris has asked to look after Granny, has taken a batch of the mules to Memphis to sell to the Union army. We learn that Granny and Ab have developed an ongoing scam. Using the original protection order from Colonel Dick and some captured U.S. letterhead, Granny forges orders requisitioning mules. Her slaves burn off the U.S. brand on the mules, and Ab sells the mules back to the army for pure profit. Ab says that they have gained hundreds of mules and more than six thousand dollars so far. As always, Granny and Ab argue about the low price he has received. It is clear she does not fully trust him because she does not store the money under the floorboards for safekeeping until he is gone, but Ab tells Granny loudly and admiringly how much he respects her cunning and her bravado.
The next morning, Ringo rides up to the house with a report on the Yankee troops in the area. Ringo and Granny mark the regiment's position on their homemade map. Thanks to his new responsibility as a scout, Ringo is more confident and assertive than ever. Ringo even refers to Ab Snopes, a white man, by his first name, though Granny corrects him. They debate about the latest prospect for a scam. Ringo thinks they should go ahead, while Granny thinks the regiment is too close to the others, making the risk too great. Ringo is a full partner in the operation. We learn that he captured the official letterhead, that he executes the forgeries, and that he and Granny dream up the false names together. They decide to go ahead, though Granny says she is worried this time. At suppertime, Granny, Bayard and Ringo ride up to the Union camp with Ab Snopes following. Ab waits behind as Granny and the boys drive to the colonel's tent, and everything seems to be running smoothly. But as soon as they leave the camp with the mules, they hear the Yankees in hot pursuit. Fortunately, Granny has already given the mules to Ab and Ringo to spirit away. The Union officer demands the mules back, but Granny feigns ignorance. It turns out that an order went out a month earlier to be on the lookout for Granny's scam. While she protests her innocence, Ringo creates a diversion in the woods. In the confusion, the Yankees all ride off after Ringo, and Granny and Bayard simply abandon the wagon and walk into the forest. After the soldiers give up, they ride away in a borrowed buggy. Ringo and Granny decide the business is finished.
At church the next day, a huge crowd of local people awaits. Brother Fortinbride, a Confederate private-turned-Methodist preacher, delivers the Sunday service. The service is short, since there are few encouraging words to be said about the war any longer. Afterwards, Granny declares her sins and asks the congregation to pray for her. Ringo then fetches her account book, and she calls up each member of the congregation in turn. We learn that Granny has been loaning the mules and her profits to the country folk, checking each week to ensure they are using them for good purposes. Ab Snopes arrives later in the day to tell Granny that the Northern armies have left Mississippi for good—by coincidence, she requisitioned the last batch of mules possible.
One day, a Union lieutenant rides up toward the house. He is the same lieutenant who has pursued them to retrieve the mules, and the last soldier they would ever see in wartime, Bayard notes in retrospect. The lieutenant's men have come to retrieve the stolen mules; he is carrying copies of every forged order Ringo has written. The lieutenant is furious, but he says that he is on evacuation orders and has only come to retrieve U.S. property. The lieutenant gives Granny a voucher for the fence his men have destroyed. He is nervous, since he would be responsible for any debts incurred by a forgery that Granny might carry out. Granny assures him he need not worry. When he leaves, she and the boys go to the church, and she prays long and sincerely for forgiveness, yet with a defiant air: "I did not sin for gain or for greed I sinned first for justice." Ringo informs Granny that it was Ab Snopes who betrayed her.
Several months pass—it is Christmastime. Ab Snopes tells Granny about a group of former Confederates called Grumby's Independents who are ravaging the countryside and frightening women and children. Ab convinces Granny to forge an order from the Confederate general Nathan Bedford Forrest requisitioning the gang's valuable horses. He tells her that even if the scheme fails, Southern men would not harm a woman. Ringo and Bayard beg her not to, but Ab is too persuasive, and Granny and the boys set off for the gang's hideout, an abandoned cotton compress. At the crossroads, Bayard tries to physically hold her back, but as he sobs, she frees herself and enters the building. Looking back, Bayard berates himself for letting her go; after a few minutes, he and Ringo run after her. They enter the compress, smell the gunpowder and find Granny's collapsed, dead body on the floor.
"Riposte in Tertio" is a fencing term that refers to a kind of counterthrust one makes after parrying an opponent's thrust. In the terms of the story, the riposte is Granny's mule-stealing operation, a response to the Yankee invasion of the South. This chapter elevates Granny to her most central role yet: before "Riposte," she and Bayard are dual protagonists, but this chapter makes Granny the most important character. At several points the narration stresses how, despite the fact that she is an old woman, she is every bit as much a warrior as Colonel Sartoris, and possibly a more admirable one. An impressed Ab Snopes tells her that the colonel cannot hold a candle to her, that she harasses the Union army more effectively without the benefit of an armed troop. Later, the Union lieutenant who comes to the Sartoris plantation to collect the mules asks her to tell him, "man to man," how many mules she has managed to steal. This ironic tribute emphasizes the comparison between Granny and the male Confederates who are the lieutenant's normal enemies. The narrator frequently notes Granny's physical frailty—the novel describes her littleness alongside the lieutenant, and the thinness of her arm as she and Bayard escape into the woods. These details draw a contrast with the effectiveness of her opposition.