Following the catastrophic event known as the Sixty Minute War, humanity's remnants have come together to create mobile "predator" cities that ruthlessly hunt and absorb their smaller counterparts in a brutal survival practice referred to as "Municipal Darwinism." This intense struggle for existence unfolds across the Great Hunting Ground, which encompasses both Great Britain and Continental Europe. In stark contrast, the Anti-Traction League has emerged, championing a way of life built upon static settlements in Asia, protected by the formidable Shield Wall. Meanwhile, treasures of the lost technology era, such as toasters and smartphones, are regarded as "Old-Tech."
In this chaotic world, the city of London captures the mining town of Salzhaken, assimilating its inhabitants and resources at the behest of Lord Mayor Magnus Crome (Patrick Malahide). Among the townspeople is Hester Shaw (Hera Hilmar), a masked woman driven by vengeance who wishes to assassinate Thaddeus Valentine (Hugo Weaving), the Head of the Guild of Historians. While this turbulent backdrop unfolds, Tom Natsworthy (Robert Sheehan), a young Apprentice Historian, is dispatched to London’s "Gut" to gather Old-Tech for the city's museum, accompanied by Valentine's dutiful daughter, Katherine (Leila George). Along the way, they uncover that civilizational destruction is linked to quantum weapons known as MEDUSA—remnants of chaos left behind from the war.
The plot thickens when Hester attempts to carry out her plan to eliminate Valentine. However, Tom intervenes, following her down a waste chute where she manages to escape but leaves behind a chilling revelation: Valentine murdered her mother and left her with a permanent scar. When Tom shares this information with Valentine, he finds himself betrayed and pushed down the very chute he tried to prevent Hester from tumbling into. A witness to this treachery is Bevis Pod, a citizen of London (Ronan Raftery), who sees the truth of what occurred.
Amidst these events, Valentine crafts a narrative for Katherine, claiming that Tom fell due to an altercation with Hester. Under lock and key, Tom and Hester eventually find themselves in Scuttlebug—a town that initially appears as a refuge but becomes a trap when the townsfolk intend to sell them into slavery. Hester divulges the brutality of her past: Valentine killed her archaeologist mother, Pandora, seeking to steal a piece of Old-Tech found in the Dead Continent of the Americas. In a shocking twist of fate, Valentine releases Shrike (Stephen Lang), a reanimated cyborg also known as a "Stalker," from imprisonment to pursue Hester.
In the tumultuous slave market of Rustwater, an Anti-Traction League agent named Anna Fang (Jihae) comes to Tom and Hester's rescue. In the ensuing chaos, Hester reveals her connection to Shrike, who once sheltered her when she was just eight years old. Despite promising to become a Stalker like him, she fled upon discovering the dangers of London’s ambitions. Back in London, Katherine grows increasingly alienated from her father, especially after learning from Bevis that Valentine was responsible for Tom's fall. The truth behind Valentine's motives becomes bleaker as he proposes an energy device project that threatens to annihilate the Shield Wall protecting Asian cities.
As Hester and Tom journey on Anna's airship, the Jenny Haniver, toward Airhaven, they align with other Anti-Traction League members. Their mission becomes clear: the weapon Pandora discovered is indeed MEDUSA—a weapon capable of obliterating cities. Realizing the impending disaster, they strategize to defend the Shield Wall, but not before Shrike catches up with them and a battle ensues that devastates Airhaven.
In a moment of poignant bravery, Shrike acknowledges Hester’s love for Tom before succumbing to his injuries. Meanwhile, Valentine orchestrates a coup against Crome, rallying Londoners behind the promise of conquest over the Shield Wall and the treasures waiting in Asia. With Anna and the Governor, Kwan, they prepare for a full-scale assault against London. As tensions peak, Hester discovers that her mother's necklace conceals a fail-safe for MEDUSA.
The climax of the story unfolds with Hester, Tom, and their allies leading a daring raid against London. They infiltrate St. Paul's Cathedral where a fierce duel erupts between Hester and Valentine. Mortally wounding Anna during their confrontation, Valentine exposes the shocking truth: he is Hester’s father. In a twist of fate, Tom intervenes, dismantling Valentine’s plans by destroying London's main engine with help from Katherine, leading to an epic confrontation where Valentine’s airship meets its tragic end beneath the weight of London itself.
In the aftermath, as the dust settles, the citizens of London, led by Katherine, find common ground with the Anti-Tractionists. Meanwhile, Tom and Hester take flight in the Jenny Haniver, embarking on a journey beyond the horrors of their past to explore the world anew.
