Season 1, Episode 8

When Clarence Clifton is murdered at a charity treasure hunt, professor Galloway believes he was the intended victim as his outfit was identical to Clarence's. Daniel Walsh, whose father was recently run over by the professor's wife, Lady Margaret, is the chief suspect. Then Margaret herself is killed after firing Thomas Dilcott -- their servant and her daughter's secret lover. The villagers suspect Daniel, but Father Brown looks closer to home for the murderer.