As Pagford Parish Council prepares for a vote on what will become of Sweetlove House - a town institution and community center serving poorer residents - chairman Howard Mollison (Michael Gambon) and his wife, Shirley (Julie McKenzie), who want to turn it into a tourist-destination spa, look to neutralize the threat of everyman council member Barry (Rory Kinnear), a solicitor and defender of the current Sweetlove House mission. When Barry's sudden death leaves a "casual vacancy" on the council, the race to fill his seat, and determine the fate of Sweetlove, stirs up drama among residents.
While Howard and Shirley push their submissive son, Miles (Rufus Jones), to run for election, Barry's friend and doctor, Parminder (Lolita Chakrabarti), rallies behind reluctant school headmaster Colin (Simon McBurney), while Barry's bullying half-brother, Simon (Richard Glover), looks to capitalize on the family tragedy. Elsewhere, Terri (Keeley Forsyth), Barry's former neighbor and a struggling meth addict, finds it hard to stay clean, while her troubled daughter, Krystal (Abigail Lawrie), takes drastic measures to help. Later, Simon's teenage son, Andrew, aka Arf (Joe Hurst), looks to expose the hypocrisy in Pagford by bringing his Uncle Barry back from the dead.