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.

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.

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.