At the Neptune Colliery in Sleescale, north-east England, veteran miner Bob Fenwick heads a group of workers who refuse to work the Scupper Flats seam because of flooding fears, though the union joins with the mine boss, Richard Barras, in dismissing any risk. During the unofficial strike, Fenwick, his proud and stoic wife Martha, and his idealistic elder son David are pulled deeper into the conflict. Denied credit by the local butcher, Ramage, hungry strikers ransack his shop; caught by the police, Fenwick is sent to jail. Three months later, the strikers' resolve has weakened. David attempts to rouse them with a speech, and determines to use his scholarship to Baddeley College, Tynecastle, to improve the miners' lot. As Fenwick is released from jail the men return to work. David leaves for university, though without his mother's support.

In Tynecastle, David runs into the cocky Joe Gowlan, once a fellow miner, now a turf accountant with eyes fixed on earning big money. At the upmarket Percy Grill restaurant, Joe surreptitiously encourages the mutual interest he spots between David and his own girlfriend, the superficial Jenny Sunley, his landlady's daughter. At the same time at another table, Joe presses his advancement with the pliant Laura Millington and her husband, mine-owner Stanley Millington.

After a speech against the private ownership of mines at Baddeley's debating society, David is approached by the local Labour MP, Harry Nugent, who offers to help him advance in politics once he gets his degree. But circumstances intervene. Abandoned by Joe, Jenny wheedles the naïve David into marriage. Needing money and a home for himself and Jenny, he abandons University for a lowly schoolmaster's job in Sleescale, secured through Barras's support. The domestic relationship quickly deteriorates: Jenny goads and jeers and wants a good time; David needs spare hours to study. A visit from David's parents proves disastrous, but there is cheerful news from football-mad Hughie, David's younger brother - picked to play in a local match to celebrate Scupper Flats' impending closure.

Relations between David and Jenny worsen when he loses his teaching position. He goes to Barras cap in hand and accepts a part-time job coaching his son Arthur; while at Barras's house he meets Joe, now a buyer for Millington's mine and secretly negotiating with Barras for coking coal, to be mined from Scupper Flats. Keen to stir the flames, Joe visits David and Jenny afterwards in his sports car; suitably impressed, Jenny feels boxed in all the more. Tumbling to the coking coal scheme, David interrupts Barras and Joe as their contract is about to be signed, and determines to stir the miners' opposition. Returning home in the early hours after consulting Nugent in Tynecastle, he finds Joe slipping out the front door and punches him to the ground. Jenny subsequently leaves him.

At a union executive meeting, David presents a strong case for official backing of the Neptune miners, but is undermined when evidence is presented of his quarrel with Gowlan. Lacking union support, the miners start working on Scupper Flats. Their fears are soon realised: a coalface detonation causes water to gush through from old flooded workings. Barras, who has been shielding a diagram detailing the flooded areas, attempts to help by phone, then joins the rescue effort with David. But a gas explosion causes further chaos. At the pit-head, families wait; the dead and injured are brought out. After six days five remain trapped: Fenwick, Hughie, 'Slogger' Gowlan (Joe's father), the religious fanatic Wept, and Pat Reedy, a youngster on his first trip underground. After suffering a stroke, Barras is carried out of the mine on a stretcher, only to die trying to struggle back with the diagram, which falls into a stream from his limp hand. Down below, the trapped miners' strength and spirits fade. Failing to blast through to them, David and the rescue party reluctantly abandon hope of finding the men. "The world's like a wheel. You're time will come," Nugent tells David, who leads his grim-faced mother home from the pit-head as other families and miners begin praying.