It's the day of the annual general meeting of Plummer & Son, makers of piquant relish. The once-thriving business has hit hard times but reluctant MD and keen ornithologist Ralph Plummer (James Fleet) promised his father he would keep it in the family.

Ralph's wife Helen wants them to consider an investment offer from rival Fieldway Foods and bickering brother and sister Anselm and Caro are keen to cash in. But they're blocked by a vote from their mother Amelia (Annette Crosbie), who earlier in the day stole a jug from Little Upton Antiques shop and had a vision of a man hanging in her garden.

A factory tour ends in tragedy when one of the visitors wanders off and is crushed against towers of bottled sauce with a forklift truck before being thrown naked into a 200-degree sterilizer.

Company director Alex Hardwick, whose parents Sam and Sonia organise the tours, is angry at having to stop production, while Anselm and Caro try to persuade Amelia to sign an Enduring Power of Attorney, anxious to secure her vote before her faculties fail.

Security guard Keith Carter reveals that Anselm returned to the factory after midnight, as police find charred clothing and a wallet in the incinerator. The dead man is identified as Dexter Lockwood, a brand executive at Fieldway Foods. All the Plummers deny knowing him.

Barnaby and Scott discover someone has been hanging a dummy from a tree at Plummer House and Dexter's father tells them about a long and bitter dispute between the two families. It looks like someone is trying to frighten Amelia.

Amelia admits to Barnaby that she once loved Dexter's grandfather Stanley but married the bullying Maurice Plummer instead, while Helen confesses she was in secret talks with Fieldway Foods. As more lies are exposed, the detectives must find out who feels strongly enough about Plummer's Relish to commit murder?