Barnaby and Jones investigate when the body of a mother is pulled from the river during the local Oak Apple carnival. Closer inspection suggests the drowning was deliberate - and as the detectives find out more about the villagers, they learn the killing could be linked to the death of the victim's daughter eight years previously.
Barnaby and Jones probe the death of a local aristocrat who seemingly died of a coronary while on the verge of making an important announcement. After the peer's will disappears and his lawyer is killed in an arson attack, it becomes clear sinister forces are at work. However, the prime suspects are the victim's family - who all appear to have cast-iron alibis for the killing.
While investigating the shooting of a council clerk, Barnaby and Jones discover he was an expert blackmailer. A phone number on the dead man's blotter sends the duo to the seaside in search of his latest targets - whose boat trip could conceal a motive for the killing. Meanwhile, Joyce is convinced a local farmer knows more than he is telling.
The Midsomer Worthy Choir are in shock after a baritone dies on the eve of a prestigious competition. Barnaby catches a figure sidling away from the church, who claims he was birdwatching at the time of the killing - but when he is fatally shot, the inspector and sidekick Jones need to find the connection between him and the cuddled singer.
The residents of Elverton-cum-Latterly gather to hold a protest meeting about proposals for a supermarket in the centre of the village, but proceedings come to a halt when the battered body of a site adviser is found. Barnaby and Jones discover the victim had a penchant for acting out role-play scenarios with locals - but that isn't the only secret the villagers are hiding.
A Midsomer Malham resident is on trial accused of battering her best friend to death, but Barnaby can't help feeling the evidence against her doesn't add up. The detective enlists the help of pensioner Mrs Beverley, who also happens to be one of the key witnesses, to find out what really happened on the night of the hug - until he realises the old lady could be at risk from his chief suspect.
The final episode of the series sees Barnaby and Jones investigating the deaths of a female pensioner and a suspect vicar, who were both killed during Broughton village's annual contest between men and women. The pair soon discover the preacher had a secret that could provide a motive - but when another body is found, they realise the answer to all the deaths lies in history.