The novel is set in South Wales during the reign of Queen Victoria. It tells the story of the Morgans, a respectable mining family of the South Wales Valleys, through the eyes of one of the sons, Huw Morgan.
Huw's academic ability sets him apart from his elder brothers and enables him to consider a future away from the dangerous coal mines. His five brothers and his father are miners. After his eldest brother, Ivor, is killed in a mining accident, Huw moves in with his sister-in-law, Bronwen, with whom he has always been in love.
One of Huw's three sisters, Angharad, marries the wealthy mine owner's son - whom she does not love - and the marriage is an unhappy one. She never overcomes her clandestine relationship with the local minister.
Huw's father is later killed in a mine explosion. After everyone Huw has known either dies or moves away, and the town is reduced to a contaminated shell, he decides to leave, and tells the story of his life just before going away.