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.

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's tenacity in helping Ned bears fruit, but not without cost. Hanson’s presence in Cornwall raises suspicion and as Demelza wrestles with how best to equip the community to look after itself, Morwenna lends herself to the cause and finds new hope.

George’s cabal moves to ruin the Poldarks, and Morwenna wrestles with a heavy decision.