In early 19th century England, a fearsome threat looms: zombies. The city of London finds itself encircled by a formidable wall and a wide moat, designed to shield the uninfected. As a reaction to the outbreak, martial arts training became a hallmark of the elite; the wealthy resorted to Japanese techniques, while the wise opted for Chinese methods. The grim history includes a catastrophic incident in 1768, when a horde of the undead crossed the royal canal and slaughtered an entire village. This prompted King George to destroy every bridge except for one: The Hingam Bridge, the lone passage across the royal canal.
In this perilous environment, the Bennet sisters—Elizabeth (Lily James), Jane (Bella Heathcote), Kitty (Suki Waterhouse), Lydia (Ellie Bamber), and Mary (Millie Brady)—have been rigorously trained in weaponry and martial arts at their father's insistence, preparing them to fend for themselves. Mrs. Bennet (Charles Dance) harbors her own ambitions, mostly focused on securing wealthy suitors for her daughters.
During a lively country dance, the Bennets encounter newcomers such as Colonel Darcy (Sam Riley), a somber figure with a knack for eliminating newly infected individuals, and his amiable friend, Charles Bingley (Douglas Booth), whose charm instantly captivates the sweet-natured Jane. Bingley’s sizeable fortune of £100,000 (equivalent to £6.7 million today) catches Mrs. Bennet's attention as she eyes him as a suitable match for Jane. As the night evolves, an unexpected zombie attack disrupts the festivities, calling the Bennet sisters into action. Amidst the chaos, Colonel Darcy reveals his expertise in zombie combat, and despite his cold demeanor, he finds himself intrigued by Elizabeth.
Afterward, Jane is perilously bitten by a zombie and falls ill from a fever. While Darcy orders her confinement, fearing infection, it turns out her condition arises from an injury caused by a misfiring musket. Throughout this tense period, Elizabeth and Darcy engage in spirited discussions about societal expectations placed on women, with Elizabeth challenging Darcy's rigid standards. The situation intensifies when the overbearing cousin, Parson Collins (Matt Smith), visits and proposes to both Jane and Elizabeth, only to be met with rejection, especially by Elizabeth, who refuses to abandon her warrior lifestyle.
The plot thickens as Elizabeth encounters George Wickham (Jack Huston), a charming soldier with a murky past linked to Darcy. Their connection grows, leading Elizabeth to share Wickham's outlandish idea of co-existing with newly “civilized” zombies. However, during a confrontation at Lady Catherine De Bourgh’s (Lena Headey) estate, it becomes clear that both Lady Catherine and Darcy do not support Wickham’s plans for peaceful coexistence.
Wickham's ulterior motive soon becomes apparent: he attempts to elope with Elizabeth, but she turns him down. In a surprising twist, Darcy confesses his love for Elizabeth, but she vehemently rejects him, angered by his actions regarding Jane. Later, Darcy writes a letter confessing his misdeeds and unraveling Wickham's deceit. As chaos ensues in London, Elizabeth learns that Wickham has absconded with Lydia.
The Bennet sisters venture across the bridge to the In-Between only to discover that the forces tasked with containing the zombie plague have failed. Elizabeth encounters Darcy fighting off zombies and reveals Wickham's treachery. The narrative reaches a climax when Darcy confronts Wickham, who reveals himself as undead, and in a fierce battle, Wickham is ultimately defeated.
As the bridge is destroyed to prevent the zombie horde from escaping London, Elizabeth professes her love for Darcy. After his recovery, Darcy anew proposes, and they share their vows in a double wedding alongside Bingley and Jane.
In a chilling mid-credits scene, Wickham is seen leading a relentless army of zombies towards their wedding ceremony, accompanied by the ominous Four Horsemen of the Zombie Apocalypse.
