The novel takes place in an alternate world where books are not works of fiction but physical vessels containing real people's memories. Binders, a class of craftspeople regarded with fear and superstition, extract painful or unbearable memories from subjects and bind them into leather-covered volumes. Once bound, the person forgets everything that was taken. If a book is burned, the memories return. The novel is divided into three parts, each told from a different perspective and timeline, gradually revealing how two young men's lives have been intertwined and torn apart by the craft of binding.
Part I follows Emmett Farmer, a young man recovering from a prolonged illness that left him screaming, hallucinating, and needing to be restrained. A letter arrives from a binder on the marshes requesting him as an apprentice. His parents insist he has no choice, despite their deep hostility toward books; Emmett recalls that his father struck him as a child for buying a book at a fair. Now, contradicting everything they have taught him, they call binding a worthy trade and send him away.
Emmett arrives at the remote bindery and meets Seredith, an ancient, white-haired woman who becomes his master. Seredith tells him he has binder's fever, an illness that strikes people with a natural calling to binding, and reveals that he actually fell ill at her bindery months earlier, though he has no memory of the visit. She teaches Emmett the physical crafts of bookbinding but withholds the deeper truth of what binding involves.
Lucian Darnay, the son of a wealthy Castleford family, arrives at the bindery seeking a binding. He addresses Emmett with an unsettling familiarity. Seredith takes Lucian into a locked room, and Emmett collapses into a five-day relapse of violent terrors. Afterward, Emmett is plagued by nightmares of Lucian that feel as though they are trying to tell him something he cannot grasp.
A woman named Milly is brought to the bindery by a desperate companion in a state of severe distress, and Emmett witnesses Seredith perform a binding for the first time. Milly emerges calm but eerily blank. When Milly's father arrives with a group of men, enraged that she was bound without his permission and threatening to burn the bindery, Emmett confronts them alone, speaking in a strange voice that seems not entirely his own. A sudden rainstorm drives them away.
Seredith reveals the truth about binding: Binders take memories, the worst and most unbearable ones, and bind them so they can do no more harm. She insists this is a sacred calling. While Seredith is ill, Emmett unlocks the binding room and sits in it. The darkness and fear that have plagued him finally recede, and the shadows at the edges of his vision vanish.
Seredith's estranged son, de Havilland, arrives from Castleford. He pressures Seredith to surrender her books, but she refuses, accusing him of selling true bindings, the original memory-books of living people, without their owners' consent. Emmett discovers de Havilland raiding Seredith's vault, and among the books he glimpses a gray-green silk volume with the name Lucian Darnay on the spine. Seredith dies, and de Havilland takes possession of everything, moving Emmett to his Castleford bindery.
De Havilland sends Emmett to perform his first binding on Nell, a maidservant in the Darnay household. When Emmett touches Nell, the binding begins involuntarily: He is swept into her memories and experiences her life of sexual abuse by Lucian's father, Piers Darnay. Lucian reveals that Piers keeps shelves of servants' books, bound over and over, and that binders enable this cycle. Among the books, Lucian finds a creamy white volume bearing the name EMMETT FARMER. Emmett seizes the book and throws it into the fire. His memories flood back violently, and he collapses.
Part II shifts backward in time, revealing the memories bound into Emmett's book. Emmett's sister Alta deliberately fell through thin ice at old castle ruins, and Lucian, staying nearby as his uncle Lord Archimbolt's guest, rescued her. Alta became infatuated and pressured Emmett to invite Lucian back. Lucian began visiting the farm regularly, ostensibly to see Alta and to adopt a terrier puppy named Splotch. Emmett's parents encouraged the connection, hoping Lucian would marry Alta. A grudging friendship developed between the two young men. At Wakening Fair, Lucian revealed what books truly are: stolen memories sold for entertainment.
On Midsummer Day, Lucian told Emmett he had been thinking about proposing to Alta. When Emmett asked him not to, Lucian kissed him. They began a secret love affair, and Lucian gave Emmett a silver ring originally bought for Alta but chosen with Emmett in mind. Alta discovered them together and told their parents, who were devastated and demanded Emmett never touch another man again.
Piers Darnay's agent, Acre, arrived at the farm offering money to have Emmett bound, promising to erase all memories of Lucian. Emmett refused. Acre resorted to coercion: He lured Emmett to a crossroads with a forged note, revealed Alta beaten and semiconscious in a cart, and had his associate kill Splotch in front of Emmett, threatening further harm. Broken and terrified, Emmett agreed. He was taken to Seredith's bindery, where she extracted all his memories of Lucian.
Part III shifts to Lucian's first-person perspective, beginning immediately after Emmett burns his book. Piers arrives and has the unconscious Emmett carried away. Lucian tries to warn Nell of Piers's abuse, but the binding prevents her from processing the information. Piers demonstrates this futility, then reveals that Lucian himself has been bound. Nell later dies by suicide. Piers shows no remorse, using Lucian's unknown book as leverage for silence.
Lucian's engagement to Honor Ormonde, his fiancée, proceeds. Emmett visits Lucian and urges him to find his book, but every time Emmett tries to explain, Lucian's perception goes blank, a hallmark of the binding's protective mechanism. Lucian threatens Emmett and sends him away. Driven by the need to find his book, Lucian goes to de Havilland's bindery and learns Emmett has been dismissed. Lucian lies to his father, claiming de Havilland is producing unauthorized copies of books. Piers sends agents to attack de Havilland, and during the assault Lucian steals the vault key, hoping it opens the marsh bindery's vault.
Lucian finds Emmett on Library Row, Castleford's street of binderies and booksellers, freezing and destitute. They ride through the night to the marsh bindery, but when they open the vault, it is empty. They spend a night together before Lucian leaves at dawn without saying goodbye, returning for his wedding.
On his wedding day, Lucian notices Lord Latworthy, a wealthy aristocrat who moves in Piers Darnay's social circle and collects bound books, watching him with an intimate, knowing expression and realizes Latworthy has read his book. Panicking, Lucian walks out of the ceremony. Outside the town hall, he encounters Emmett, who realizes the book must be in Latworthy's private library, having once delivered books there while working for de Havilland. They gain entrance to the estate and find Lucian's gray-green book locked behind an iron grille. A stray ember ignites displaced books, and the fire spreads rapidly because books containing memories are inherently unstable. Lucian runs into the flames, terrified his bound memories contain something as monstrous as his father's crimes.
The fire consumes Lucian's book, and his memories flood back: meeting Emmett, falling in love, the ring, and the forced separation. He discovers that what he had been bound to forget was not some terrible crime but his love for Emmett. They escape the burning library through a window. In a summer house on the grounds, Lucian confirms he remembers everything. Around them, the fire releases the stolen memories of countless people. Emmett takes Lucian's hand, and they leave together.