DCI Barnaby and Sgt Scott find themselves investigating the bizarre murder of a young, wealthy landowner, Gareth Heldman. Gareth's lifeless body is discovered on the riverbank, with an unusual stab wound to his thigh. Bruising on his body indicates he got into a fight just before his death. Gareth was last seen arguing with local business owner, the beautiful Vanessa Stone.


Investigations turn to riverbank keeper Nathan Green. Not only is he Vanessa Stone's boyfriend, but he's also sporting a suspicious black eye.


When DCI Barnaby discovers that the murder weapon is in fact a missing ancient Celtic spearhead and that Gareth's thigh injury is consistent with an ancient ritual, they rely on David Hartley-Read for more information. David has just released a book based on his dead father's archaeological work that focuses on the Celtic history of Midsomer. Before his death, David's father, Paul Hartley-Read, made claims that he actually uncovered the ancient Celtic spearhead along with a challis from a site at Midsomer Barrow over 30 years ago.


As the Midsomer Barrow site is situated on Heldman land, David was in discussions with Gareth, hoping to get permission from Gareth's mother Anne to hold an ancient Celtic festival at the site. Anne is reluctant, given that her husband Roger, died accidentally at the site around the same time the claims of the challis and spearhead were made.


But things don't add up, Barnaby and Scott find themselves trying to unravel the circumstances of Roger Heldman's death 30 years ago. They reveal that Roger was a notorious womaniser and that his death was no accident. Could there be a link between the murder of Roger Heldman and that of his son, 30 years later?


When David Hartley-Read is shockingly murdered in front of dozens of people including Barnaby and Scott, their investigation moves up a step and uncovers a maze of twisted relationships, professional jealousies and lies festering in the picturesque village community.