Moon and Son - Season 1 Episode 4 Where No Birds Sing

A metal-detectorist finds a plate with astrological symbols on an ancient site and asks Gladys to help him identify it. His visit is followed by another from a sinister ex-military man asking uncomfortable questions. Gladys enquires into the origins of the plate - for which she has to recruit Trevor, with whom she has fallen out. They arrive at the site to find Eavis dealing with the detectorist's death in a microlight accident. Then Gladys's contact at the local museum is found dead, and Gladys herself is accused of theft. Investigating in an attempt to clear her name, she is taken prisoner by her sinister visitor of earlier. Trevor and Cecile, meanwhile, are looking for a man who was billeted locally during the War; it seems the local people are covering up after a massacre of escaping German POWs, whose bodies are buried at the archaeological site. Trevor rushes to rescue Gladys, but her kidnapper is shot dead by the elderly officer he has been trying to protect.