Huw Morgan, the academically inclined youngest son in a proud family of Welsh coal miners, witnesses the tumultuous events of his young life during a period of rapid social change. At the dawn of the 20th-century, a miners' strike divides the Morgans: the sons demand improvements, and the father doesn't want to rock the boat.
A crippled Huw, youngest son of patriarch Gwilym Morgan, is told that he will one day walk, while his eldest brother battles for a union in the mines, to their father's chagrin.
Huw is bullied on his first day of school; Ianto receives surprising help from the Reverend, concerning the creation of a work union at the mines.
The mine owner's son Iestyn Evans courts Angharad to the chagrin of Ifor. Meanwhile, Dai Bando teaches Huw how to fight his bullies; however, standing up for himself only gets Huw punished by pompous teacher Mr Jonas.
Angharad is engaged to Iestyn Evans, so Bronwen consults Reverend Gruffydd's help to intercede.
Celebrations abound after Ifor and his choir return from singing for Queen Victoria; Ceinwen Lloyd takes Huw for a moonlit stroll on the mountainside; Angharad's marriage to Iestyn begins to crumble.
As Bronwen mourns Ifor, who dies in the mines as he shows Huw the ropes, Owen and Blodwen's romance blossoms; meanwhile, Huw attempts to reconnect with Angharad, who refuses to visit her family.