The woman, Agnes Aubert, returns to her damaged cat shelter, Les Amis des Chats, on Rue Sainte-Roseline. The building is cold and has a large hole in the wall from the magicians’ duel. She is greeted by her two personal cats: His Majesty, a large, tyrannical black cat, and Banshee, a nonsensical, voiceless tabby. 

In addition to Agnes’s two cats, the shelter is straining to care for 48 other cats, an all-time high. Agnes finds that her sister, Élise, has left her a porcini mushroom pie in a spiced cream sauce. As she prepares for bed, Agnes reflects on her late husband, Robin, who died two years prior. His Majesty had been especially fond of Robin and still misses him. Overwhelmed by financial pressure and her grief, Agnes falls asleep.

Agnes and her sister, Élise, view another potential shop with a landlord named Mathieu. To avoid another rejection, Élise claims that they run a typing service, a lie that makes Agnes deeply uncomfortable. 

During their conversation, Mathieu mentions that the infamous magician Havelock Renard, known as the Witch King, might have been responsible for the powerful explosion on Rue Sainte-Roseline. Mathieu is impressed enough to offer Agnes and Élise the shop, but he makes the rental contingent on a reference from Hamad, the man who owned the sandwich shop next to Agnes’s old shelter. Realizing that Hamad will immediately expose their lie, Agnes abruptly withdraws their application, claiming the space is too small for their needs, and walks away.

Upset after the failed viewing, Agnes wanders and finds herself on Rue des Hirondelles. Out of a sense of reckless curiosity, she decides to investigate the disreputable shop M. Levasseur had warned her against. She first enters the neighboring bookstore, where the owner, Oksana, gives her a cryptic warning to stay away. 

Undeterred, Agnes goes to the vacant shop and is greeted by a nervous young man named Yannick Abrams, who identifies himself as the landlord’s representative. The shop is spacious, historic, and comes with an opulent upstairs apartment for a suspiciously low rent. Yannick explains that the most recent tenant, a scarf importer, left without notice, and the one before that, a baker, abandoned his pies in the window display and vanished. 

As he tours her around the shop, Yannick warns Agnes not to use the trapdoor to the basement, claiming it is unsafe. Agnes notices that the curtains had suddenly closed when they went upstairs, yet no one had come in the door, an unsettling detail she cannot explain. Despite her unease, her desperation leaves her no choice, and she agrees to rent the shop.

While walking home, Agnes concludes that the shop on Rue des Hirondelles must have been an illegal magic shop that sold Artefacts, cursed items that allow magicians to channel magic from another realm. She theorizes that either a lingering curse or the shop’s reputation is what frightens tenants away. 

Agnes’s internal debate is cut short when she discovers two small, abandoned kittens on the street. She gathers them into her coat pockets to take them back to the shelter. The immediate need to provide a home for the kittens solidifies her resolve, erasing any remaining doubts about moving into the mysterious and potentially dangerous new location.

Agnes, Élise, and their volunteer, Mina, move into the new shelter, bringing their total number of cats to 52. Yannick arrives to help, and they repurpose the expensive scarves left by the previous tenant as cat blankets. 

Soon after, their first strange visitor arrives: A woman in an unidentifiable fur coat who speaks briefly to Agnes, then disappears into the back room near the basement trapdoor. Later, a detective named Laurent Rouzet stops by, indicating that he is merely welcoming Agnes to the neighborhood. His presence makes Mina visibly nervous. Laurent explains he has been trying to contact the absentee landlord and asks Agnes to let him know if the owner appears. To avoid further police presence at the shelter, Agnes awkwardly suggests they meet at a nearby café instead, which the flustered detective misinterprets as a romantic invitation before making a hasty departure.

After a week in the new shop, Agnes observes more strange phenomena. The old baker’s oven inexplicably smells of fresh pastries every morning, and she regularly hears thumping noises from the basement. A series of wealthy, mysterious visitors begin to frequent the shelter, using it as a passageway to access the basement via the trapdoor in the back room. 

Agnes and Élise decide the disturbances are a tolerable nuisance. Agnes now believes her landlord is a magician who secretly lives and works in the basement. She seeks information from the neighboring bookseller, Oksana, who responds obliquely, saying she knows all her neighbors, including those who do not wish to be known. She also indicates that magicians like cats, which Agnes takes a sign confirming her suspicion. Oksana explains she warned Agnes away because she looked like the type to cooperate with the police, and reveals that Detective Laurent has been investigating the shop for nearly a year.

One night, during a snowstorm, a powerful magician named Valérie breaks into the shelter. She is looking for a man named “Lock,” whom she identifies as her brother, Havelock Renard, the infamous Witch King. To force him out of hiding, Valérie begins magically tearing the shop apart. 

In response, a shadow-monster emerges from the basement trapdoor, collides with Valérie, and knocks her down; it then vanishes, and Havelock becomes visible standing by the broken back door, barefoot and dressed in pajamas. He and Valérie engage in a fierce magical duel. During the fight, Valérie summons a dragon-like creature from a paper bird that swallows Havelock whole; he bursts free in a shower of paper birds. 

Havelock is shocked to discover his shop has been turned into a cat shelter, calling the animals “vermin.” He ultimately defeats Valérie by casting a spell that hurls her out into the storm. Knowing she will soon return, he declares he must magically relocate the entire building. As Havelock prepares the spell, Agnes frantically runs outside to rescue two cats, Fantôme and Lynx, who escaped during the chaos. She returns just as Havelock casts his spell, and the world splits in two.