Dwight and Caroline face heartbreak before flooding at the mines puts a life in danger; Ossie plots to have Morwenna put in an asylum; Rowella's husband becomes suspicious.

With the rising price of grain, working men find themselves struggling to support their families; Ross's failed efforts in Westminster see him advised to use a more nuanced approach.

Nathaniel Pearce's death illuminates how he embezzled Pascoe's clients' funds; in London, Ross discovers that Geoffrey Charles has been led astray by Adderley and must steer him away from trouble before Elizabeth finds out.

The Poldarks, Enyses, and Warleggans take part in some of London's distractions; George dotes on Elizabeth due to his excitement of a potential an heir; Lady Whitworth has a physician agree to place Morwenna in an asylum.

To persuade George that Valentine is his child, Elizabeth obtains a tonic to induce her labour. Meanwhile, Ross attempts to mend his relationship with Demelza.

The Poldarks look forward to life together in peace, but a plea from his old army colonel compels Ross to the capital. Arriving in London, he finds a city gripped with paranoia, and is determined to save Ned.

Demelza and the kids accompany Ross in London, but his attempts to clear Ned's name leads them into a dangerous situation.

Cecily and Geoffrey Charles' relationship continues to blossom, while her father pursues an arrangement with George; Hanson's unexpected presence in Cornwall raises suspicion.

Ross is given hope for the Despards' return to Honduras, but finds his new nemesis, Ralph Hanson, has returned to Truro. Demelza continues to help the community help itself, and Dwight gains unexpected patients.

Ross returns to London with the Despards and Enyses in the hope of securing Ned and Kitty's return to Honduras at last; when the banks start issuing paper notes instead of gold, Demelza finds herself thrown into uncharted waters with her workers.

Ross throws himself into fighting for Ned's liberty as George prepares to marry Cecily and finalise his deal with Hanson and Merceron. Geoffrey Charles is forced to make a desperate plan to elope with Cecily before the wedding.