The Watchmaker of Filigree Street

Set in 1880s London against the backdrop of Irish nationalist bombings and a rapidly modernizing Japan, the novel follows three characters whose lives become entangled around a mysterious gold pocket watch, a brilliant clockwork maker, and the question of whether the future can be known.

In November 1883, Thaniel Steepleton, a telegraph operator at the Home Office in Whitehall, receives a message from Superintendent Williamson at Scotland Yard: Clan na Gael, a violent Irish nationalist group, has promised to detonate bombs in all public buildings on May 30, 1884. That night, Thaniel returns to his boarding house to find his door ajar and the kettle hot, though nothing has been stolen. On his pillow sits a velvet box containing a gold pocket watch that is warm to the touch but refuses to open. His widowed sister Annabel in Edinburgh denies sending it, and a pawnbroker refuses to buy it, claiming watches by this maker mysteriously vanish. Through the winter and spring, the watch remains locked while Thaniel fills out will papers, preparing for what may be his death.

A parallel storyline introduces Grace Carrow, a fourth-year physics student at Oxford who disguises herself in men's clothes to access the university library, where women are barred without escorts. Grace is building an interferometer, a device designed to detect the luminiferous ether, a hypothetical substance through which light was believed to travel. Her friend Akira Matsumoto, the charming son of a Japanese nobleman, teases her about her lack of social graces. Without a successful experiment, Grace faces either an unwanted marriage or a life teaching schoolgirls. Her mother pressures her to attend a Foreign Office ball and consider Francis Fanshaw, a widowed family friend, as a husband.

On May 30, the watch's clasp unlocks by itself, revealing a working glass face and a watchpaper reading "K. Mori, 27 Filigree Street, Knightsbridge." That evening, the watch emits a terrible siren that forces Thaniel out of the Rising Sun pub moments before a bomb destroys Scotland Yard. Shaken but alive, Thaniel travels to Knightsbridge to find the watchmaker's shop.

Keita Mori, a small Japanese man with dyed blond hair and a northern English accent, greets Thaniel with two cups of tea, as if expecting him. His workshop overflows with extraordinary clockwork, from bronze birds to a magnetic solar system model. He introduces Thaniel to Katsu, a clockwork octopus of astonishing lifelike quality, and claims the watch was stolen months ago. Too exhausted to leave, Thaniel stays the night.

A flashback to Hagi, Japan, in 1871 reveals Mori's past. He secretly aided Ito, the Minister of the Interior, in compelling his cousin Lord Takahiro to sell the Mori clan's castle to the central government. Takahiro punished Mori violently for the interference. That evening, an unstable castle wall collapsed and killed Takahiro; Mori showed no surprise. He joined Ito's staff but insisted he must leave in exactly ten years to meet "someone" in London.

Back in London, Williamson tasks Thaniel with spying on Mori. A consulting watchmaker named Frederick Spindle examines both the watch and the bomb's remains, reporting that both share Mori's distinctive bimetallic mainsprings, pointing toward Mori as the bombmaker. Thaniel moves into Mori's spare room and takes a new position at the Foreign Office Japan desk. He searches Mori's bedroom and finds a strange book filled with entries about events that have not yet happened, written in ink years before their dates.

At the Foreign Office ball, Thaniel meets Grace. During a piano recital, he recognizes the second movement as a piece Mori plays every morning, though the composer insists it is brand new. That night, Mori reveals his ability: He does not see the future but remembers it, the way ordinary people remember the past. Likely events feel vivid; unlikely ones are hazy. When something becomes impossible, the memory vanishes. He offers testable predictions, and every one comes true.

Grace devises a blind test, bringing a tampered deck of cards with an extra ace of spades. Mori removes the extra card without hesitation and wins at poker but loses at backgammon, where outcomes depend on random dice rolls. Working through the night, Grace realizes that her interferometer's failure does not disprove ether but proves it is stationary at ground level. She theorizes that ether particles are disturbed by electrical impulses from human thought and that a clairvoyant could sense these disturbances, though random processes produce waves carrying no predictive information. She sends Thaniel a telegram confirming Mori is genuine.

When police raid Mori's workshop, Thaniel forces the officers to withdraw by threatening to contact the Foreign Office about the wrongful arrest of a Japanese nobleman. Afterward, composer Arthur Sullivan hears Thaniel tune a piano and offers him the pianist position for a new operetta, The Mikado. Thaniel realizes Mori deliberately detuned the piano weeks earlier to engineer this opportunity.

Grace and Thaniel arrange a marriage of convenience: She gains her aunt's Kensington house and its cellar for a laboratory, and Thaniel's nephews can attend school on the dowry money. Mori provides a ring but refuses to attend the wedding. A second flashback to Tokyo in 1882 reveals that Mori silently eliminated multiple assassins targeting Ito by arranging lethal coincidences months in advance. When Ito discovered this, Mori used knowledge of Ito's wife's deadly allergy to bee stings to force Ito to let him leave for England.

On the wedding night, Thaniel leaves Grace at their hotel and returns to Filigree Street, where he kisses Mori in the darkened workshop. Grace arrives to find Thaniel alone and assumes Mori has just been there. She confronts Thaniel, warning that Mori is manipulating him. Grace stages a fake kidnapping at the hotel, steals Katsu, and uses coin tosses to decide her path, evading Mori's foresight through randomness. She knocks Mori unconscious in an underground tunnel, rigs Katsu with stolen chemicals from a firework shop, and releases the octopus in the show village. Its random gears carry the makeshift bomb to an unpredictable location, invisible to Mori's clairvoyance.

At the debut of The Mikado, Yuki, a nationalist teenager from the show village, attempts to shoot Minister Ito. Thaniel tackles him. Mori, injured from the underground, carries a weather vial to the rooftop and releases it, triggering a rainstorm to prevent fire from spreading. The firework shop explodes, the blast races up the elevator shaft, and Mori is blown off the roof.

Both survive. In the hospital garden, Thaniel confronts Grace: He recognized the sound of Katsu in the elevator shaft and deduced her scheme. She admits she intended the explosion to turn Thaniel against Mori, not to kill anyone. Their marriage is annulled. Thaniel leads Williamson to Spindle, who confesses that Clan na Gael coerced him into building the bombs. Spindle is arrested.

At a ceremony honoring Thaniel for saving Ito, Grace attends in black, mourning her mother's recent death. Matsumoto invites her to stay at his family's castle in Japan, and she accepts. Grace notices Mori flipping a heavy bolt identical to one that fell from Matsumoto's train; it remains ambiguous whether Mori arranged the incident to keep them apart or bring them together. Thaniel returns to Filigree Street with Mori, who brings Six, an orphan girl he hired from the workhouse, home permanently. Mori reveals he always knew Spindle was the bombmaker but kept silent because the revelation would have driven Thaniel away. The novel closes with Thaniel and Mori in the workshop, surrounded by clockwork forests and phosphorescent constellations.