In her manuscript, Nuria recalls meeting Julián Carax in autumn 1933 while working for the publisher Toni Cabestany, who has been issuing Carax’s French-written novels in Spanish despite disastrous sales. Suspicious calls keep requesting Carax’s address, so Nuria deletes it from the files. She later discovers the print runs are secretly bankrolled by Miquel Moliner, with Cabestany profiting from inflated invoices; when Nuria confronts Moliner, he confirms he knows and urgently warns her never to reveal Carax’s address.

Nuria and Moliner become close friends, bonded by books and by Moliner’s devotion to Carax, his childhood friend. Moliner confesses he loves Nuria, but Nuria cannot return it; Moliner tells her she is in love with Carax without realizing it. When Cabestany’s gout prevents him from traveling, Nuria is sent to Paris to negotiate renewals with Gallimard and to collect Carax’s new manuscript, The Cathedral Thief, and Carax invites her to stay in his cramped Saint-Germain attic.

In Paris, Nuria is startled by Carax’s prematurely aged, exhausted appearance and his bare, book-stuffed life, shared with a large white cat, Kurtz. She notices the manuscript’s dedication, “For P,” but refrains from reading. Carax keeps her entertained with stories and evasion, then assigns a devoted boy, Hervé, to guide her through her publishing meetings, revealing how Carax quietly supports the orphan and others around him despite his own poverty.

During a sleepless night, Nuria finally asks who “P” is, and Carax answers Penélope, describing her as the only woman he ever loved. He recounts how, in 1921, Irene Marceau found him sick and amnesiac, saved him, and gave him work playing piano in her hostess house while pushing him to keep writing. As Nuria presses why he never returned to Barcelona for Penélope, Carax breaks down, and the intimacy between them shifts into a wordless sexual relationship that lasts through Nuria’s extended stay.

Nuria falls deeply in love while recognizing Carax remains emotionally bound to Penélope, which breeds jealousy and despair. After buying Carax a costly fountain pen he has long admired, Nuria meets Irene, who wordlessly confirms Carax has been “waiting” for someone else; Nuria realizes Carax will never be hers. Nuria leaves Carax abruptly—placing the pen on his typewriter, taking the manuscript, and departing as Monsieur Darcieu ominously remarks she has “poison in the heart”—and she sees Carax on the platform as her train departs for Barcelona on her twenty-fourth birthday.