Pride and Prejudice and Zombies takes place in 19th century England where a zombie virus has spread across the country. Those with the zombie virus are called the "stricken", "sorry stricken", "un-dead", "unmentionables", or "zombies". The presence of the zombies adds a horror element to its fiction genre.
The protagonist of the story is Miss Elizabeth Bennet, a young woman living with her parents, Mr. and Mrs. Bennet, and her four sisters. Mr. Bennet trains his daughters in martial arts and weapons training, eventually molding them into a capable zombie-fighting army. Meanwhile, Mrs. Bennet endeavors to obtain wealthy and high status husbands for her daughters. Seeing an opportunity to achieve her goal, Mrs. Bennet sends her daughters to a local ball where a wealthy bachelor, Charles Bingley, is expected to make an appearance. At the ball, Mr. Bingley and the eldest Bennet daughter, Jane, make a connection in the midst of a chaotic zombie attack. During this time, Elizabeth meets Fitzwilliam Darcy, Mr. Bingley's closest friend/zombie killer.
As time passes, Mr. Bingley and Jane become more acquainted with one another. However, this companionship leaves the Bennet girls confused when Mr. Bingley & Co. suddenly abandon Netherfield Park. When the local militia arrives in town to exhume and destroy dead bodies, Elizabeth becomes friendly with one of the soldiers, George Wickham, who claims that Darcy cheated Wickham out of an inheritance.
Elizabeth's dislike for Darcy intensifies when she learns that he plotted to separate Bingley from her sister, Jane. Elizabeth vows to avenge the separation of her family by killing Darcy, and she is afforded that opportunity when he appears unannounced at a cottage where she is visiting her newlywed friend Charlotte. Before Elizabeth can fetch her katana and behead him, Darcy surprises her by proposing marriage. In this scene, they break out into a verbal and physical fight, in which Darcy is wounded. He escapes with his life and writes a long letter to Elizabeth explaining his actions. He separated Jane and Bingley out of fear that Jane had contracted the "mysterious plague". In regards to the allegedly wronged soldier Wickham, Darcy explains that Wickham attempted to elope with Darcy's younger sister to take her considerable fortune – this was the "inheritance" that Wickham had claimed. Elizabeth realizes that she has judged Darcy too harshly and is humbled. Darcy realizes that his demeanor encourages people to believe the rumors about him and resolves to act more appropriately.
Elizabeth embarks on a trip around the country with her aunt and uncle, fighting zombies along the way. At Pemberley she encounters Darcy, who repels a horde of zombies. Darcy's changed attitude and manners impress Elizabeth and lead her to consider reconciling their relationship. However, that deliberation is crushed when her younger sister Lydia elopes with Wickham in London. The Bennet family fears the worst when they receive word that Wickham and Lydia have married, following an "accident" that has left Wickham as a quadriplegic. After visiting the Bennets, the couple moves to Ireland. Elizabeth eventually discovers that it was Darcy who engineered the union, thus saving the Bennet family from ruin.
Darcy and Bingley return to the countryside, and Bingley resumes courting Jane. Elizabeth hopes to renew her relationship with Darcy, but his aunt, the Lady Catherine, interferes and insists that her daughter Anne is a better match for her nephew. Lady Catherine challenges Elizabeth to a duel, committed to eliminating the competition, but Elizabeth defeats her. Elizabeth spares Catherine's life. Darcy is touched by this gesture and returns to Elizabeth. They then marry and begin a long and happy future together, insofar as the ever-present threat of zombie apocalypse permits.