The Casual Vacancy by J.K. Rowling begins with the death of Barry Fairbrother, a Pagford Parish councillor. Barry dies of an aneurysm at the carpark of the golf course's restaurant on the eve of his nineteenth wedding anniversary.

The following morning provides glimpses into the townspeople's reactions to Barry's death. Barry held a seat as a Pagford Parish Councillor and was fighting to keep the neighborhood known as the Fields a part of Pagford. Prior to his death, he was working with the local newspaper to illustrate the positive influence that allowing the children of the Fields. He grew up in the Fields and knew that by attending school in Pagford's good schools allowed him a better life that he would have had had he had to go to school in Yarvil. Additionally, the Bellchapel Addiction Clinic rents a small church to administer methadone to addicts that live in the Fields and Yarvil. Pagford Parish, specifically Howard and Shirley Mollison, no longer wants to lease the building to this tenant.

In the following weeks, an election is held to fill Fairbrother's casual vacancy on the council. During the days leading up to the election, mysterious posts appear in the name of the Ghost of Barry Fairbrother on the parish website, which Shirley Mollison is in charge of. The messages are defamatory toward the candidates who are running: Simon Price, Colin Wall, and Parminder Jawanda. Although the people feel they are being attacked by other people in the town, ironically, they are being attacked by their own teenage children.

As the debate to keep the Bellchapel Addiction Clinic heats up and Miles Mollison wins the vacant seat, each family lives in their own crisis. Desparete to get out of her terrible living situation, Krystal Weedon runs away with her younger brother Robbie. While she is having intercourse, in the hopes of getting pregnant, with Fats Walls, her younger brother falls into the river and drowns. That Sunday morning, as many of the adults in town are out walking and contemplating their own melodramas, they saw Robbie, a toddler, wandering alone and dirty, but do nothing.

The only person brave and sincere enough to help was Sukhvinder Jawanda who jumps in the river to save Robbie while risking her life. Krystal Weedon now realizes that there is no way out of this life. Without her brother and feeling the guilt of his death, she chooses to commit suicide.

Howard Mollison has a heart attack the same afternoon that Robbie Weedon drowns and Shirley Mollison, after learning about his long-term affair with co-worker Maureen, plans to attack him with an epipen. He has a heart attack first and now she fears that he knew that she was going to attack him.

The novel ends with the funeral of Robbie and Krystal Weedon who comes from a family that changes the least in the story since they are used to death and tragedy. The other character's contemplate their futures as they are reminded of the chaos that has ensued since Barry Fairbrother's death.