Metropolitan Police Sergeant Nicholas Angel is reassigned to the rural town of Sandford, Gloucestershire. Angel arrests Danny Butterman for drunk driving, but later discovers that he is the son of Inspector Frank Butterman, and a police officer himself. Angel is frustrated by the mundanity of the village, his incompetent colleagues, and Frank's and the Neighbourhood Watch Alliance (NWA)'s prioritisation of low crime statistics over law enforcement.

Angel and Danny stop the two lead actors of a local production of Romeo and Juliet for speeding. A cloaked figure later murders them, and their deaths are staged as a car crash; only Angel suspects foul play. He and Danny discover an illegal weapons stash, including an old sea mine, and confiscate it. Angel warms to Danny, and together they binge-watch action films at Danny's house. That night, a cloaked figure attacks George Merchant, a wealthy land developer, in his home, and kills him in a gas explosion. Angel suspects that the deaths are connected to a recent property deal.

A local journalist, Tim Messenger, approaches Angel at a village fête, claiming to have information. However, a cloaked figure kills Messenger by dislodging masonry from the church's tower. Angel learns from Leslie Tiller, the village florist, about her plans to sell her land to Merchant's business partners. While Angel retrieves his notebook, a cloaked figure murders Tiller with her garden shears. Angel pursues the killer, but to no avail. Angel suspects Simon Skinner, a supermarket manager, as the property deal would have built a rival supermarket, but Skinner has an alibi.

After surmising that there are multiple killers, Angel is attacked in his hotel room by Michael "Lurch" Armstrong, an employee of Skinner. He incapacitates him and learns about a secret NWA meeting at Sandford Castle. There, the NWA, led by Frank, reveals that they committed the murders and staged them as accidents, as each victim threatened Sandford's chances of winning "Village of the Year". Irene, Frank's late wife and Danny's mother, put everything into helping Sandford win the first-ever competition, but travellers ruined their chances the night before the adjudicators arrived, driving her to suicide. Frank has since vowed to help Sandford win Village of the Year every year, whatever the cost. Angel flees but stumbles into the castle's catacombs, discovering the corpses of the NWA's victims, some of whom Angel had helped arrest or question. Danny suddenly appears and feigns murdering Angel and, pretending to dispose of him, unsuccessfully urges him to return to London for his own safety. After arming himself with the confiscated guns, he and Danny engage in a shootout with the NWA. When Frank orders the other officers to arrest them, the pair successfully convinces them of Frank's complicity.

Frank flees, and the officers besiege the supermarket, with Skinner escaping in a police car with Frank. After he and Danny engage the offenders in a high-speed chase and shootout, Angel corners Skinner at Sandford's model village. After a fight, Skinner is impaled on a miniature church steeple. Frank attempts to escape in Angel's car, but a swan that the pair had recaptured earlier attacks him. Angel's former superiors arrive and ask him to return to London as the crime rate has risen heavily in his absence, but Angel declines, electing to remain in Sandford.

While the officers are reviewing the paperwork of the many arrests, Tom Weaver, the last NWA member, enters the station wielding a blunderbuss. He shoots at Angel, but Danny takes the bullet. In the resulting struggle, Weaver accidentally activates the sea mine, killing himself and destroying the station. One year later, Angel has been promoted to Inspector, and Danny, having survived, has been promoted to Sergeant. After visiting Irene's grave, the two drive to their next crime scene.