Crowner John is summoned to investigate the murder of a tin miner. The victim worked for Devon's most powerful and successful mine owner, Walter Knapman. There seems, to be only one motive - to sabotage Walter's business. But the tinners have their own laws, and they are none too pleased at Crowner John's interference. How on earth can Crowner John sort all this out when his own life is in turmoil?