Murder comes in the form of possible mistaken identity in "Death and Dust" from season 10.
Delyth Mostin and Jim Kirkwood are older lovers planning to be married. She is divorced and he is a widower. The match is met with opposition. For one thing, Delyth's children are practically having nervous breakdowns over it; Delyth rejected a local farmer who is obviously unhappy with the union; Kirkwood's ex-mother-in-law thinks he might have had hurried his wife's death from cancer. Then there is Delyth's volatile ex-husband, who lives in Wales.
On the home front, Joyce and Cully want to enlarge the patio; also, Cully's serious boyfriend is around, and he's afraid Barnaby doesn't like him.
Good episode, but the best part for me was the Welsh scenery, in part viewed from a helicopter. It's absolutely stunning. The scenery is always good in the show, with its pretty towns and houses, but the terrain here is something to see.