A hole in the ground, such as the air vent of a defunct Cornish tin mine, could lend itself to sinister uses. Martin Filton is a Cambridge medical student when he first encounters the mysterious affair at Tregellick. Afraid of being laughed he doesn't go to the police with his story of shots fired, the gory bundle he had retrieved when it fell from a jeep, and how, a little later, he discovered a piece of the same bloodstained sacking caught on the wire fence round `the hole'. But no-one was ever reported missing at Tregellick, much less there being any rumour of murder. The whole thing lies fallow at the back of Martin's mind until, twenty years later, taking a break from his career as a surgeon, he returns to Cornwall and meets Drina. Her home was the farm to which the jeep was going; her `aunt', sister of Drina's foster-mother, had been its driver. The puzzle of Drina's parentage and the unhappiness this caused her spurs Martin into investigation both of that mystery and the curious events of that autumn day long ago.