When Debbie Moffett is crushed to death with a giant round of cheese at the home of the world-famous Midsomer Blue, secret and controversial plans to modernise the dairy are revealed while rumours about private lives of the parents cause a row at the prestigious local prep school. As other people linked to the dairy meet agonising deaths, long-held secrets start to emerge.
DCI Barnaby and DS Jones investigate the death of Debbie Moffett, who is found dead at the cheese factory where she worked. She had recently had a run-in with Beatrix Ordish at the Midsomer Pastures prep school after they advised her that her daughter would not be welcome at the school the next term. She was also having an affair with the woman's husband, Oliver. The cheese factory itself was famous for producing Midsomer Blue Cheese, but has been unable to make a profit for some time now. In trying to reduce costs, the owners have upset local milk producers, including Helen Caxton. Several subsequent murders do little to clarify things. Barnaby sees a connection among the various murders however and it leads him to the killer.
- Neil Dudgeon as DCI John Barnaby
- Jason Hughes as DS Ben Jones
- Fiona Dolman as Sarah Barnaby
- Tamzin Malleson as Kate Wilding
- Hattie Morahan as Hayley Brantner
- Patrick Robinson as Gregory Brantner
- Lucy Liemann as Beatrix Ordish
- Richard Dillane as Oliver Ordish
- Eloise Webb as Poppy Ordish
- Martine McCutcheon as Debbie Moffett
- Maggie Steed as Sylvia Mountford
- Con O'Neill as Jim Caxton
- Kate Ashfield as Helen Caxton
- Jesse Fox as Jake Yapley
- Isabella Blake-Thomas as Holly
- Sian Clifford as PC Milton
- Mike Ray as CID Officer
- Pamela Betsy Cooper as Dairy Farm Worker (uncredited)
- Chris Cowlin as CID Officer (uncredited)
- Sarah Dorsett as PTA Parent (uncredited)
- Anthony Farrelly as C.I.D. Officer (uncredited)
- Susan Fordham as CID Officer (uncredited)
- Richard Herdman as School Handyman (uncredited)
- Pete Meads as Cyclist (uncredited)
- June Smith as Bar Maid (uncredited)
- Gillian Steventon as Holly's Gran (uncredited)
- Last appearance of DS Ben Jones.
- No credit is given for the actor that plays Phil Caxton.