Ross decides to reopen the family copper mine Wheal Leisure and persuades Francis to help him. Ross also escorts Francis's put-upon sister Verity to a dance, where he crosses swords with George Warleggan, annoyed that Ross borrowed capital for the mining project from a rival bank to that of his uncle. Verity meets the sea captain Andrew Blamey, who is keen to marry her but George forbids it, claiming that Blamey killed his first wife. The relationship ends when Francis challenges Blamey to a duel, in which Francis is injured, though Demelza proves her worth when she tends to him, impressing Ross.

Ross reopens Wheal Leisure, drawing his work force from Charles' mine and winning the respect of his tenants. Whilst he and Demelza are at a local wedding Elizabeth gives birth to a son, Geoffrey Charles. Ross attends the christening , noting not only the growing friendship between George Warleggan and Francis but overhearing gossips speculate on his relationship with Demelza. He is genuinely impressed by her efficiency and starts to confide in her. One of his workers, young father Jim Carter, is taken to court for poaching and Ross speaks on his behalf but fails to prevent the boy being sent to prison. Drunk and miserable he returns home and ends up in bed with the comforting Demelza. Next day he is visited by a sympathetic Elizabeth, clearly unhappy in her marriage. Seeing them together Demelza prepares to leave but Ross urges her to stay and they get married.

The news of Demelza and Poldark's marriage spreads through the community, threatening Wheal Leisure's prospects.

Wedding bells ring as miner Mark Daniel marries visiting actress Keren Smith whilst Demelza and Ross have their own celebration as their daughter Julia is born, Ross not allowing Demelza's father's unwelcome visit to the christening party to ruin matters. Young Dr Dwight Enys comes to the area and is befriended by Ross. He is progressive and philanthropic, which annoys the curmudgeonly incumbent Dr Choake. With widespread poverty and mine closures all around Ross proposes that the pit owners form a collective with their own smelting company, to beat the Warleggans' monopoly, and presses ahead with the scheme. Francis opts out and is subsequently ruined as his mine is forced to close. To repay Verity for her kindness Demelza reunites her with Andrew Blamey in town, where they witness a food riot by starving locals.

Whilst Ross's cooperative has some success there are hard times throughout Cornwall and typhoid sweeps through Bodmin jail and kills Jim Carter just as Ross and Dwight break in to rescue him. Dwight is also called upon to visit the injured Keren, who throws herself shamelessly at the young doctor, as Demelza notices. Untouched by privation the Warleggans throw a ball where Francis, struggling to accept his reduced circumstances, neglects Elizabeth, allowing George to step in as her escort. Ross turns up drunk and confronts Halse, the magistrate who jailed Jim and then plays cards recklessly though he does expose his opponent as a card sharp, known to the Warleggans, who are now all the more determined to break him. Further scandal is caused by the arrival of Captain Blamey, who asks Verity to run away with him.

Ross faces ruin as, along with the rest of his collective, he must sell to the Warleggans' company at a nominal price. At the same time the disease known as putrid throat sweeps through the county, claiming many lives and Dwight, still contrite over Keren, throws himself into trying to treat it. Elizabeth and her family are stricken and Demelza goes to help them but infects herself and her daughter with disastrous results. Divine justice appears to intervene as the Warleggans' ship and its cargo founder on the rocks and Ross leads the villagers in collecting its spoils from the beach. Demelza recovers from her sickness, only to face another setback to her marriage.

Ross chairs the meeting for his mine's share-holders, where expansion of Wheal Leisure is approved but Warleggan's spy Tankard is also present and Warleggan's heavies attack Jud for failing to discredit Ross at his trial after their payment to commit perjury. To remain solvent the Poldarks are forced to sell many of their possessions and livestock, causing Demelza to keep her pregnancy secret from her husband. However, following the attack on Jud, Ross realizes Warleggan has schemed to keep Francis and himself at odds and is reconciled with his cousin at a family party, after which Demelza reveals her pregnancy to a far from displeased Ross.

Aware of her husband's infidelity with Elizabeth Demelza does not hold back from expressing her disgust and defiantly attends a house party alone. Here she flirts with the amorous captain McNeil though loyalty to Ross causes her to draw the line at sex with him. Elizabeth's marriage to Warleggan finally goes ahead whilst Ross gets good news on the business front when repayment of a previous loan enables him to maintain the mine and a profitable find is made - one which will hopefully save his marriage.