Ross and Demelza look to forget the past and rebuild their marriage, but new arrivals threaten their fragile reconciliation.

Sam and Drake provoke Trentishoe and Ross's stubbornness gives George the upper hand. Meanwhile, a great naval battle leaves Dwight's fate in question.

Ross is ordered to leave Roscoff under threat of execution. He travels with Tholly to meet his contact in France, but finds information about Dwight's fate comes at a high price. Sam leads a congregation of methodists in protest outside the church - only to face broken promises from George, who revokes their lease on the meeting house, which leads them to turn to Elizabeth for help. Geoffrey Charles has some words of advice for Drake, who has shared a moment of intimacy on the beach with Morwenna.

George proves merciless as the new magistrate, and Clowance is christened. Ross discovers the means to both help Dwight and combat Cornwall's famine.

While George makes political manoeuvres at home, Ross sails to France to rescue Dwight from the French Revolution.

Drake finds himself in the Warleggans' firing line as George moves to secure his connection to the nobility, and Ross provides some local aid.

George pursues a vacant seat in Parliament as Agatha plans for her hundredth birthday, and Ross is given a proposition. Meanwhile, there is a new arrival at the Whitworth vicarage.

Ross is adamant George will lose in the election and determines to get a headstone made for Agatha's grave, something Trenwith has neglected. George, meanwhile, questions Dwight over Valentine's legitimacy and - paranoid and jealous - shuts himself to Elizabeth, as Rowella begins to seduce Osborne Whitworth and Demelza receives tokens of Hugh's affection. Sam continues to pine after Emma, as Dwight instructs Osborne to forego intercourse with Morwenna and Cary informs Lord Falmouth that the Warleggans will be opposing Falmouth in the election. Ross returns from his mine to discover Hugh Armitage at Nampara with Demelza - and this time Hugh's attention does not go unnoticed..

The Poldark family finds itself challenged on all fronts and threatened as never before.

As the Poldarks look to rebuild their marriage and the Enyses to increase their family, Cornwall struggles under the Warleggans, whose power threatens all they hold dear.

The Poldarks determine to get their relationship on track and the Enyses announce they're expecting a baby. Hugh's worsening health threatens his chance to stand in the election, and the prospect of him remaining in Cornwall adds pressure to the Poldarks' fragile marriage. At the Sawle Feast, Tom Harry challenges Sam to a wrestling match. When Emma offers herself as the prize, Sam accepts.

Ross faces the challenge of Parliament and the Warleggans refuse to accept defeat. In Cornwall, Demelza contends with a failing mine and fixing Drake's broken heart. Dwight and Caroline welcome a baby daughter. Ossie meanwhile tends to a dying parishioner and George hosts an extravagant party at Trenwith.

Ross is reunited with his family at home, but tragedy strikes in Cornwall. Dwight tells Caroline some devastating news about Sarah. Ossie is seen visiting Rowella by her husband Arthur, who grows suspicious. Emma returns to give Sam her answer, whilst Drake is persuaded into courting Rosina.

George increases the strain on the struggling poor, driving Ross to make a risky gambit. The adversity the Poldarks face, however, may not be confined to Cornwall alone.

After it is revealed that Nathaniel Pearce embezzled Pascoe’s client’s funds, the Warleggans take action. In London, Ross finds Geoffrey Charles led astray by Adderley. Sam convinces Drake to return from exile following his abandonment of Rosina and Morwenna’s subsequent rejection and Morwenna reveals some news. Dwight meanwhile helps in the development of Truro’s infirmary.

Joining the Enyses and Ross in London Demelza enjoys the city life and accompanies Ross to a charity ball thrown by Warleggan to celebrate his wife's pregnancy. Here she attracts Adderley's predatory attention, leading him to challenge Ross to a duel, the outcome of which makes Warleggan even more anxious to crush Ross. Whilst Demelza, overwhelmed by events, returns to Cornwall, Morwenna has a message for Drake and Geoffrey Charles makes an observation.

Ross Poldark returns home after American Revolutionary War and rebuilds his life with a new business venture, making new enemies and finding a new love where he least expects it.