Annie Woodrow, a charity worker from Midsomer Malham, is standing trial for killing her best friend, Frances Trevelyan, in a case that Barnaby had investigated ten months previously. But he becomes increasingly unsettled that the prosecution's case doesn't match the facts. Barnaby & Jones enlist the help of key witness Mrs Beverly in a risky entrapment to find out what really happened. Jones's promotion to Det Sgt comes through at the same time.