Ross and friends embark on another expedition in attempt to free Dr. Enys from French prison. George tries to elevate himself by disparaging Ross. Morwenna finally decides her feelings for Drake aren't worth the potential repercussions.

Whitworth's sexual demands on Morwenna are making her life a misery. When she falls pregnant he brings in her sister Rowella to help her, a girl who immediately spots his weakness. To give the broken Drake a positive in his life, Ross sets him up with his own smithy. At the Enys's public union both Elizabeth and Demelza notice Morwenna's unhappiness. Warleggan is perturbed when Hugh's uncle, Lord Falmouth, singles Ross out as a hero, and Sir Francis Bassett, declaring him a man of the people, proposes him as a member of parliament. Ross declines, allowing Warleggan to assume the candidacy, much to the annoyance of Demelza, who becomes closer to the besotted Hugh Armitage. Aunt Agatha dies, but her final act is to suggest to Warleggan that Ross is the true father of his son Valentine.

Agatha's dying words have the desired effect on Warleggan, who vents his anger by freezing out his wife and son, and dismissing more mine workers, whom the kindly Ross then employs. Warleggan succeeds in becoming a member of parliament. Elizabeth and Ross, in a chance encounter at Agatha's grave, discuss the parentage of Valentine. Dwight has his suspicions about Whitworth's sexual abuse of Morwenna, but Rowella is more than happy to take her sister's place in the parson's bed. Demelza, aware that Hugh is smitten with her, and feeling neglected by Ross, begins to succumb to the handsome naval officer, whilst Lord Falmouth summons Ross as his champion.

Times are hard for the locals as grain is being sold to the highest bidders abroad. A corn riot breaks out in Truro, and the Carne boys, innocent bystanders, are among those arrested. MP George Warleggan manipulates the trial against them, but Ross does his best to save them, impressing Sir Francis Basset, who wants him to stand in the upcoming election. Demelza is torn between her admirer, Hugh Armitage and Ross, but she and Ross look to rebuild their marriage. Caroline has good news for Dwight, while Morwenna continues to endure life with her husband.

With Hugh's rapidly failing health eliminating him from standing in the election, his uncle, Lord Falmouth, thanks to Caroline and Demelza, joins with Sir Francis in agreeing that Ross should oppose Warleggan as the prospective member of parliament for the district. The result is a triumph for justice but Demelza must make an admission to Ross and, for her brothers, the path of true love continues to run anything but smoothly.

Ross is now member of parliament for Truro and making compassionate speeches opposing slavery and the use of child workers. Inevitably Warleggan, smarting from his defeat, links up with the disreputable Monk Adderley for revenge on Ross and a seat of his own whilst Whitworth seeks another way to discredit him. Returning to Cornwall, where Caroline has given birth to a daughter Sarah, Ross is called upon to save an ailing mine and also pays a visit to Elizabeth.

Caroline and Dwight suffer a family tragedy, prompting her to take unusual action. Dwight also confounds Whitworth's attempt to commit Morwenna to an asylum, to allow him to continue his affair with her sister Rowella and proves himself a hero when blasting causes heavy flooding at the mine. This last event causes Ross to doubt a return to parliament but is persuaded by Dwight to change his mind. Warleggan also enables his political ambitions to come to crooked fruition.

In parliament Ross achieves some success on behalf of his constituents. He also meets Caroline, who has fled her recent tragedy and who introduces him to Monk Adderley. Back in Cornwall there is famine and sickness. However Morwenna and Drake are afforded a second chance when Whitworth's sins catch up with him although Drake, having broken off his wedding to Rosina Hoblyn, comes under suspicion.

Warleggan is triumphant to discover that the late Nathaniel Pearce embezzled money from Pascoe's, the bank used by Ross. With Ross in London - impressing prime minister Pitt - Demelza attempts to save the bank but fails and Warleggan takes full advantage to plot further. Drake is dissuaded from leaving the area by Sam but Morwenna still rejects him whilst Caroline returns from London with Ross for the opening of Dwight's new infirmary. Here Ross makes an impassioned speech which leads to the bank being saved. He also has a surprise for Demelza whilst Elizabeth has news of her own.

Now suspicious about Valentine's paternity after Geoffrey Charles' observation, Warleggan is cold towards Elizabeth and, to force an early delivery of her unborn child to allay further suspicions about Ross being Valentine's father, she takes drastic measures - which do not end well. Drake, however, is overjoyed when Morwenna agrees to marry him whilst Lord Falmouth refuses to accept Ross's resignation from Parliament because of his duel with Monk Adderley.