Octogenarian Felicity Law puts a little-known painting by landscape artist Henry Hogson up for auction. Bidding is fierce between Patricia Blackshaw of the Hogson Society and frozen food businessman Alan Best. But the winner is Texan art collector George Arlington who pays a record £400,000 for the masterpiece, Bishop's Drift.


Patricia is furious, but Felicity announces she is giving the proceeds to the Arnold Simms School of Art, run by his pretty daughter Matilda. The school works with criminals but recently lost its funding - thanks to councillor Neville Blackshaw, Patricia's husband.


Matilda returns home to find her house has been broken into - she phones Felicity to tell her the 'black book' has been stolen and warns her to be careful. Later that night, Felicity is tortured and killed.


Patricia reveals to the police that Felicity was once Arnold Simms' lover, while local crook, and Matilda's former lover, Graham Spate offers greedy art dealer Anthony Prideaux another Hogson. That night, Alan Best's beloved Midsomer Meadow is stolen.


Matilda takes a smitten Barnaby on a research tour of Hogson's countryside; later he meets Christine Miller, who claims to be a New York fund manager who loves Hogson. But Jones discovers she's an art insurer from Fulham, trying to recover Best's painting.


Using Jones' knowledge of rare breed pigs, Barnaby realises Best's picture is a forgery. With Christine's help, they discover Prideaux is trying to sell it. He tells them that Spate has it, but when the police get to his house Spate is dead and Midsomer Meadow is sprayed with blood. Best admits Spate bribed him into taking part in an insurance scam.


Then the detectives discover Bishop's Drift is a forgery too. They confront Matilda who admits her father was the forger and she sold a 'masterpiece' whenever they needed cash. The records were kept in her black book - something that Spate knew all about.


Barnaby confronts Arlington who can't accept he's been fooled. But when Prideaux, too, is murdered, he confesses the dealer had demanded a million pounds not to reveal his collection of Hogson's were fakes. Barnaby and Jones persuade the Texan millionaire to put up £2 million to get the black book back. But can they solve the mystery and catch the killer?