Tristram's mother reveals a voyeuristic curiosity in her desire to watch through the keyhole as Uncle Toby makes his march for Widow Wadman's heart. Corporal Trim has had some difficulty in getting Toby's ragged clothing and old wig tidied up; fortunately, Tristram tells us, Toby's goodness of heart shines forth in his countenance to such a degree that he looks good in anything. The advance begins, but then Toby and Trim detain themselves outside Mrs. Wadman's door while Trim tells of his brother Tom, who married a widowed Jewish sausage-maker in Lisbon and was taken into custody by the Inquisition. Walter and Mrs. Shandy watch impatiently during this lengthy delay.
The author pauses to review what he has written, deciding that "upon this page and the five following, a good deal of heterogeneous matter [must] be inserted, to keep up that just balance betwixt wisdom and folly, without which a book would not hold together a single year." He then expostulates for several chapters on the nature of his writing, defending himself in particular against charges of indecency. As evidence for the cleanness of his writing he submits his extensive laundry bills. Tristram plans a digression, and then realizes that in talking about it he has actually committed it. Marveling at this fact, he returns to Uncle Toby.
Mrs. Wadman and Bridget wait inside, poised for the knock at the door. Toby has a moment of nervous hesitation, but before he can tell Trim to wait, "Trim let fall the rapper." They enter the house, and two blank pages appear in the place of the next two chapters. We rejoin the action in the midst of a suggestive conversation in which Toby offers to let Widow Wadman see and touch the place where his groin was wounded.
Tristram cites Slawkenbergius on how a woman chooses her husband and discusses Mrs. Wadman's reservations about Uncle Toby's "fitness for the marriage state"--which, he assures us, was perfectly fine in spite of the wounded groin. Bridget has engaged herself to find out the details of the injury on her mistress's behalf, resolving to be as friendly with Trim as necessary in order to secure that vital information.
Tristram balks just at the moment of arriving at "the choicest morsel of what I had to offer to the world," suddenly falling into doubt about his literary powers. He invokes the spirit of Cervantes to aid him, and is reminded then of his travels through France and Italy. Anguished to realize that nobody else will appreciate the necessity of leaving chapters 18 and 19 blank until chapter 25 is completed, he voices again his favorite plea to the world "to let people tell their stories their own way." He then explains the details of what transpires in those omitted pages. Toby declares his love, and Widow Wadman, after an awkward pause, turns the conversation to the subject of children. Toby, who does not understand the motive behind her questioning, covers his bafflement by proposing marriage. Back in chapter 26, Widow Wadman interrogates Toby about his wound, and he admires the "humanity" of her solicitude. When she asks where, exactly, he received the blow, he sends for the map of Namur and sets her finger on the very place.
Trim then retrieves the map and makes the same geographical explanation to Bridget. She cuts to the chase, telling him bluntly the rumor she has heard about Toby's impotence; Trim denies the allegation. He successfully romances Bridget, and for a while the two separate phases of the campaign continue regularly every afternoon. Trim finally reveals to his master the true reason behind Widow Wadman's concern for his injured parts, and Toby is woefully disillusioned. The whole neighborhood, meanwhile, has learned of their misunderstanding, and Walter is highly indignant on his brother's behalf. The novel ends with the story of a cock and a bull.
At the end of the fourth volume Tristram writes, "The thing I lament is, that things have crowded so in upon me, that I have not been able to get into that part of my work, towards which I have all the way looked forwards, with so much earnest desire; and that is the campaigns, but especially the amours of my uncle Toby." Tristram finally leads us to the long-promised conclusion of his Uncle Toby's affair, and at last we learn the reason behind Toby's much-vaunted modesty.
Toby's nervousness and innocence is endearing, and the presentation of the love affair as a battle seems in many ways a more apt use of the military metaphor than all their fruitless and obsessive hobbies. The story of Trim's brother Tom and his successful courtship serves in one way as an inspiration to Toby's efforts. On the other hand, the mention of the Inquisition leaves a lingering suggestion of the marriage state as a kind of prison, contributing to Toby's hesitancy. The prison metaphor certainly also extends to the question of censorship and hovers over Tristram's digression into the question of indecency in his writing.
The unhappy end to the Wadman affair recalls Toby's confession, in Volume 2, that he understands "nothing at all" about women. His naivete here confirms that fact, but it also induces a somewhat bleak answer to the implicit question of what the nature of women actually is. Walter's lecture on the lustfulness of women, just before the novel ends, is a conclusion to his unfinished oration on the same topic earlier in the book. Women seem to bear the brunt of blame and contempt here, especially in light of the attention devoted earlier in the volume to cataloguing Mrs. Shandy's faults. Trim actually makes a more sympathetic statement when he suggests that women are often "put upon...'to please others more than themselves.'" Walter's final speech is so out of tune with the playful attitude the book as a whole takes toward sexuality that we cannot imagine the author endorsing such a view. Where women fit into Sterne's intricate treatment of sexuality and gender remains a complicated question.
The issues of fertility, sterility, and sexuality dominate the closing chapters, bringing the focus back to the same set of concerns with which the book began. The reference to Walter's ritualized first-Sunday-of-the-month activities creates another satisfying symmetry. The final chapter brings together all the major characters to listen to one last cock-and-bull story, effecting a self-ironical reprise that serves as the author's farewell.