In an alternate 18th-century Britain, a brilliant but controversial experiment reshapes the boundaries between life and death. A scientist named Victor Frankenstein allegedly discovers a method to reanimate a corpse with a soul that can think, feel, and speak. When his first creation is destroyed, a second approach emerges: Necroware, a programmable artificial soul that can upgrade like software, though its users still struggle with speech, thought, and autonomy. By the 19th century, corpses become a cornerstone of labor, their powers expanded by a gleaming machine called the Analytical Engine, built on the ideas of Charles Babbage.
John Watson, a medical student and aspiring corpse engineer, illegally crafts his own Necroware to resurrect his deceased friend, Friday, and he dreams of a fuller restoration. But his unauthorized project is quickly discovered by M [Akio Otsuka], a shadowy figure in the British Secret Service. To avoid punishment, Watson agrees to work as an agent for the Empire, charged with locating The Memorandum—Frankenstein’s original notes on reanimating a corpse with a soul. The search leads him to Alexei Karamazov [Shin-ichiro Miki], a Russian corpse engineer hiding in Kabul with fragments of the forbidden research.
Accompanying Watson are Captain Frederick Burnaby [Taiten Kusunoki], his loyal bodyguard, and their guide, Nikolai Krasotkin [Daiki Yamashita]. Their journey plunges them into a dangerous frontier where upgraded corpses—now capable of limited human-like thought—attempt to outwit them at every turn. A perilous rescue comes from Hadaly Lilith [Kana Hanazawa], the enigmatic secretary of former U.S. President Ulysses S. Grant [Koji Ishii], who quickly becomes a pivotal ally. When one advanced corpse briefly regains its memory and voice, the group realizes the stakes are far bigger than a single life restored.
The expedition reaches Kabul and then traverses toward the perilous Khyber Pass, where Karamazov’s ambitions grow darker. Watson and Friday witness Nikolai being forcibly upgraded while still alive, a conversion that kills him and sparks the creation of an even more intelligent corpse. In a brutal turn, Karamazov dies by his own hand after revealing that The Memorandum might lie in distant Japan, urging Watson to destroy it rather than let Frankenstein’s work fall into the wrong hands.
In Tokyo, the hints converge as Watson teams up with Yamazawa Seigo [Jiro Saito] of the Imperial Japanese Army. They learn The Memorandum is in the hands of Osato Chemical, a sprawling firm with shadows that reach deep into the night. As they close in, they face waves of upgraded corpses, and Watson is forced to weigh the risk of study against the urgent need to destroy the dangerous knowledge. He hesitates at a crucial moment, studying the notes instead of destroying them, and a fire erupts in the building. In the smoke, a mysterious figure takes The Memorandum, revealing himself as Frankenstein’s original creation—the One [Takayuki Sugo]—still intelligent after a century and more dangerous than ever.
Aboard the USS Richmond, Watson is carried toward America for treatment, with Hadaly and Burnaby at his side and Grant's faction pressing for action. The voyage becomes a test of loyalty and humanity as Friday, now chained due to his unpredictable violence, wrestles with the memory of his restored self. In San Francisco, The One leverages The Memorandum to broadcast a signal that awakens corpses to attack humans—and even the ship’s own crew—sparking a violent chase across city streets and sewers. Hadaly reveals a deeper truth: she is an artificial lifeform with the power to control corpses through sound and a longing for a soul of her own. Her bond with Watson grows as they fight to resist The One’s totalizing plan.
Grant is killed when a detonating corpse bursts through defenses, and the group follows Hadaly to a hidden safehouse where she and Burnaby briefly part ways with Watson and Friday. The moment Friday nearly turns on Watson, a glimpse of hope appears as Friday hesitates, allowing Watson to subdue him. At Hadaly’s sanctuary, Watson completes the delicate work of healing Friday’s condition, making him immune to The Memorandum’s signal.
Meanwhile, The One is captured by M, who intends to weaponize Frankenstein’s creation to end all wars by turning every human into a corpse. He is brought to the Tower of London, where his mind faces the combined scrutiny of Charles Babbage’s preserved intellect and Frankenstein’s own brain, creating a surge of power that could expand the signal and overwhelm any resistance. The protagonists retaliate with a submarine assault on Traitors’ Gate, and Burnaby’s distraction buys time for Watson, Hadaly, and Friday to confront The One. Hadaly uses her abilities to suppress him, while Friday wrests control of Babbage to sever the signal’s reach. Yet M’s shot strikes Hadaly, and The One escapes, killing M, overpowering Hadaly, and seizing Friday.
The One’s grand design is revealed: he intends to merge all the primordial minds into a single, true human mind, and to fashion a bride promised by Frankenstein himself. Using The Memorandum, Babbage, and Frankenstein’s brain, he calls forth a composite soul, inserting it into Hadaly while transferring his own essence into Friday. Burnaby’s intervention damages Babbage, forcing The One to retreat into his own body as Friday helps Watson seal him within The Memorandum, destroying the Tower in the process. In the aftermath, Watson envisions a future where Hadaly might truly carry a soul, urging him not to abandon the dream of resurrecting Friday.
Back at the original workshop, Watson and Friday begin a new collaboration, blending Karamazov’s methods with surviving pages of The Memorandum to perform an extraordinary, unknown corpse upgrade on Friday. Four years later, a post-credits scene shows Watson fleeing with a new companion, Sherlock Holmes, while Burnaby and Hadaly—now going by the name Irene Adler—watch from a nearby rooftop, with a still-recovered Friday observing the scene from a distance. The tale ends with a lingering suggestion: the line between life and death remains tender, and the road to a true, human-like soul may still lie ahead for those who dare to dream it.
