On the Calculation of Volume I

The novel is narrated by Tara Selter, an antiquarian book dealer trapped in a single endlessly repeating day. The narrative opens on her 121st eighteenth of November, with Tara hiding in the guest room of her house in Clairon-sous-Bois, a small town in northern France. She listens as her husband, Thomas Selter, moves through his morning routine: filling a kettle, making tea, opening the fridge. Thomas does not know she is in the house; he believes she is away on a business trip in Paris. Every night Tara goes to sleep and every morning she wakes to the same date. Thomas remembers life through November 17th but experiences each eighteenth of November as though it is the first, with no memory of any repeated day.

Tara recounts the events leading to the fracture. The couple co-owns T. & T. Selter, a business specializing in illustrated eighteenth-century books. On November 17th, she traveled to Bordeaux for an annual auction, then continued to Paris and checked into the Hôtel du Lison on the rue Almageste. She called Thomas, and they discussed her finds and her plan to visit a research librarian on the nineteenth. The next day, the 18th, she visited bookshops and bought several works, then called on their friend Philip Maurel, a dealer in ancient Roman coins. Philip introduced her to his new girlfriend and assistant, Marie, and the three spent the evening eating and drinking at the shop counter. When Tara and Marie dragged a dusty gas heater from the back room to warm the space, Tara burned her hand badly on the red-hot metal.

The following morning, Tara discovers the fracture. At breakfast, the newspaper is the same one she read the day before. Her certainty crystallizes when she watches a fellow hotel guest drop a slice of bread in exactly the same manner as the previous day, with the same hesitation, the same disposal, the same replacement croissant. She checks the date at multiple locations: All confirm it is November 18th. She calls Thomas, who remembers only their conversation from the 17th; his entire 18th has been erased. The books she purchased that day have vanished from her room, though those bought on the 17th remain. She returns to the bookshops and finds both volumes back on the shelves, unremembered by the sellers. At Philip's shop, Marie shows no recognition. A Roman sestertius, a coin depicting Emperor Antoninus Pius and the goddess Annona, sits on the counter as before. Tara buys it as a gift for Thomas. In the back room, the gas heater sits undisturbed in its dusty corner, yet the burn on Tara's hand persists.

She calls Thomas and tells him everything. He believes her without question, but the realization that he lived a day he cannot remember triggers his own quiet panic. They debate explanations, from hallucinations to temporal loops, but none holds: The burn disproves fantasy, and the exact replication of events disproves coincidence. Tara takes a train home. Thomas meets her at the door and draws her into the warmth. She gives him the sestertius, and they sit in inherited armchairs drinking tea, carefully avoiding words like "yesterday" that they would interpret differently. Thomas suggests the problem will resolve itself. Tara goes to bed worried, tucking two of her books under the pillow as a safeguard.

She wakes to her fourth eighteenth of November. Thomas has no memory of her return. Over the following weeks, Tara learns to extend a hazy, undefined feeling upon waking, a fog that buffers the shock of recognition. She and Thomas wander through the repeating day in deep intimacy. She describes this as the happiest time of her life, a "temporal Mesopotamia" where their two different experiences of time converge. They borrow library books on parallel universes, theorize freely, and track small inconsistencies: Purchased food vanishes overnight but reappears on store shelves, library books return to their stacks, and their bank balance resets each morning, yet objects kept physically close to Tara tend to stay. The sestertius, left unattended, disappears, presumably returning to Philip's shop.

After roughly 65 days, the protective fog lifts. Each morning's explanation to Thomas sounds more inadequate. Around Day 76, she finds the accumulated distance unbearable, gathers all traces of herself, and retreats to the guest room. For five days she lies on the spare bed in a state of intense mental processing, her brain harvesting sounds and organizing patterns. On Day 81 she re-emerges and tells Thomas she needs his help to find the rift. For 27 days they investigate systematically, turning the living room into a control room of notes and graphs. They confirm that Tara's body follows progressive time while Thomas's resets each night. During an all-night vigil, Thomas loses concentration for an instant shortly after five in the morning, and his memory is wiped clean. A second attempt ends when a frying pan vanishes from the table at the same moment Thomas forgets everything. Every theory they construct collapses.

Tara concludes they cannot share the eighteenth of November. On the evening of Day 107, she dismantles the control room, restores the kitchen, and the next morning slips into the guest room before Thomas wakes. She begins writing on paper found on a shelf, recording everything she remembers. She settles into a rhythm of coexistence through sound, boiling water when Thomas flushes the toilet, leaving the house under cover of his afternoon music.

A disturbing realization takes hold: Thomas is a "ghost" who leaves no trace (his evening leek is back in the garden row by morning), while Tara is a "monster" consuming a finite world. Supermarket shelves grow barer from her cumulative purchases. She begins shopping farther afield and studying the night sky, buying a telescope on a trip to Lille. She follows Thomas on several occasions but recognizes that seeing him magnifies the loss and resolves to stop.

Tara moves into an empty house on the rue de l'Ermitage, away from Thomas's daily routes. She begins sensing another time underneath her November days: fleeting glimpses of September in the light, October in the woods where trees still hold their leaves. On Day 339, she encounters Thomas on a bench and proposes they travel to Paris together to close her circle when the year is complete. Thomas resists and suggests she go alone, trusting her sharp eyes. They spend the evening eating pizza and drinking wine; after Thomas falls asleep, Tara walks back to the rue de l'Ermitage alone.

As her year nears its end, Tara packs and takes the train to Paris. At the Hôtel du Lison, the receptionist hands her the key to Room 16 as if nothing has happened. She walks the streets with heightened alertness, cataloging every detail, searching for a variation that will signal the year has turned. On Day 366, she wakes from a dream of swimming and drifts through the city without a plan. Philip calls her name on the street, an event that never occurred on any previous eighteenth of November. He takes her to the shop, where he and Marie announce they are buying the hoarder-crammed apartment above it and open champagne to celebrate.

Emboldened, Tara tells Philip and Marie about the time loop. Philip grows skeptical. When she mentions the sestertius, he places the coin in a gift bag and hands it to her, as if to end the conversation. Tara finds herself abruptly on the street. She wanders the familiar blocks and confirms the day's usual markers, deflating her hope that Philip's unexpected appearance signaled a different day. In her hotel room, she writes that it feels as though there is a hole in her eighteenth of November, a way out she had not imagined. She resolves to leave the day open, to let herself be carried by whatever current takes her: "Now I swim. Dive."