Stuart Pridwell is killed in a rock fall after telling his wife Moira he was going to retrieve buried treasure from a disused mine shaft. Moira calls in Hetty to locate precious stones believed to be buried in one of two mine chambers but when Hetty and Geoffrey go underground they find only a locker key belonging to surly miner Jack Duckett. Duckett has been set up and the stones already taken. In identifying the culprit Hetty realises that the motive was an affair of the heart,rather than greed.
—don @ minifie-1