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.

When French ships are seen off the coast, Sir Francis appoints Ross to lead the volunteers ready to repel any invasion, to the annoyance of Warleggan. George is further angered when Sir Francis criticizes his use of his parliamentary privilege for his own benefit. He vents his rage on Drake, having him brutally assaulted and his forge destroyed. Demelza, disappointed by Ross's apparent failure to avenge her brother, spends more time with Hugh, while Ross quells a rebellion against Warleggan by agreeing to stand for parliament himself. Rowella finds herself pregnant by Whitworth, and blackmails him into paying a young local, Arthur Selway, to marry her, giving Morwenna the strength to rebel against him. Elizabeth also revolts against her cruel husband, who begins to lose his cocky self-assurance, whilst Demelza and Ross go to bed with doubts on either side.

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.

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.