Miss Marple: The Murder at the Vicarage (1986)

When a despised magistrate is found shot to death in the library of the local vicarage, his wife and her lover, a portrait painter living on the church grounds, both confess to the crime. Miss Marple's keen powers of observation clear both of them of the crime, but other suspects abound. Included are the murdered man's daughter, who posed for the artist, a neurotic cleric who's embezzled church funds, the local doctor, an ex-convict who poached on the magistrate's land, and a missionary's enigmatic widow who argued with him the day before he was killed. An exasperated Inspector Slack must reluctantly accept help from the analytical Miss Marple.