Ross prepares for his trial as Demelza and Elizabeth try to help his cause. George does everything in his power to harm Ross, Francis wrestles with his conscience, and Dwight clashes with an entitled heiress, Caroline Penvenen.

On the eve of her husband's trial Demelza ignores Ray Penvenen's advice and approaches Judge Lister for mercy but her plan is scuppered by George Warleggan. Warleggan is convinced that Ross will be found guilty but Ross is an immensely popular defendant and despite the intervention of Demelza's father and Warleggan's paid prosecution witnesses his own excellent defence, aided by the testimony of the captain whose life he saved, Dwight and surprisingly Jud, leads to an acquittal. Dwight also attends Francis following his failed suicide bid after his belief that Elizabeth had an affair with Ross and gets closer to Caroline, who is not sorry when outsider Trevaunance's election as MP causes a riot. Warleggan however is still desperate to acquire Ross's mine by any means whilst Demelza and Ross consider having another baby.

Ross chairs the meeting for his mine's share-holders, where expansion of Wheal Leisure is approved but Warleggan's spy Tankard is also present and Warleggan's heavies attack Jud for failing to discredit Ross at his trial after their payment to commit perjury. To remain solvent the Poldarks are forced to sell many of their possessions and livestock, causing Demelza to keep her pregnancy secret from her husband. However, following the attack on Jud, Ross realizes Warleggan has schemed to keep Francis and himself at odds and is reconciled with his cousin at a family party, after which Demelza reveals her pregnancy to a far from displeased Ross.

An epidemic sweeps through the county and Dwight is grateful to Caroline for providing him with a cart-load of fresh oranges to combat it. Ross meanwhile is thwarted in his efforts to expand the mine, thanks to Warleggan and his proxy, Tankard. To provide finances he strikes a deal with a local smuggler to use his beach to land cargo on, much to Demelza's annoyance. Ross also goes into partnership with Francis, despite Warleggan's attempts to split them up, and they open up the mine gaining access to Wheal Grace. Demelza gives birth to a baby boy, Jeremy, which goes some way towards reconciling Francis with Verity.

When a smuggler is caught magistrate Francis cleverly ensures a lenient sentence but Ross suspects one of his miners, Nick Vigus, as an informer. Francis is also loyal to his cousin when they meet Warleggan at a party, where Elizabeth admits that she still has affection for Ross and Caroline jilts Trevaunance before Dwight reveals his feelings for her. Francis discovers copper in the mine but his jubilation is cruelly curtailed whilst Ross once more finds himself at the mercy of Warleggan, who has obtained his promissory note and has a financial hold over him.

A cheerless Christmas looms for the Poldarks with Francis drowned in the mine having only found fool's copper and Ross facing debtor's prison if he cannot pay Warleggan. Ross is also anxious to expose the traitor and agrees to a dangerous scheme to trap them whilst Demelza is troubled by his frequent visits to console Elizabeth - though Warleggan is quick to ingratiate himself with the widow. Ray Penvenen accuses Dwight of fortune hunting and tries to ban him from seeing Caroline but she is far too perceptive and realistic to give up the man she loves. She also bails out Ross, whose tenacity she admires, in his hour of need - whilst seeking to remain anonymous.

Ross joins a smuggling trip in the Isles of Scilly in order to meet Mark Daniel but, in his absence, George moves in on Elizabeth. Caroline convinces Dwight they must elope for a new life in Bath, and Captain McNeil plans to ambush the smugglers on their return.

Ross and Dwight stand trial for their part in the smuggling. A new tin lode gives Ross renewed hope in Wheal Grace, but it is George who is there for Elizabeth when her mother falls ill and deals Ross a bitter blow.

Aware of her husband's infidelity with Elizabeth Demelza does not hold back from expressing her disgust and defiantly attends a house party alone. Here she flirts with the amorous captain McNeil though loyalty to Ross causes her to draw the line at sex with him. Elizabeth's marriage to Warleggan finally goes ahead whilst Ross gets good news on the business front when repayment of a previous loan enables him to maintain the mine and a profitable find is made - one which will hopefully save his marriage.

The mine is at last bringing Ross wealth but Demelza, still slow to forgive, goes to stay with new mother Verity. An angry Ross gives the snide Warleggan a beating after his suggestion that Ross is cheating Elizabeth's son out of his inheritance before deciding to reenlist to fight in the Napoleonic wars. Dwight also signs up as a naval surgeon but is reunited with Caroline before he sets sail. Warleggan builds fences around his property, cutting off the public right of way and Demelza is one of the casualties of his hired thugs. Irate locals march on his house, Trenwith, vowing to burn it to the ground, but Ross dissuades them to spare them prosecution before he is reconciled with Demelza.

Ross and Demelza look to forget the past and rebuild their marriage, but new arrivals threaten their fragile reconciliation.

Whilst anxious to build their own Methodist chapel, the Carne brothers work well at the mine, though they defy Ross by entering Warleggan's estate, where Drake meets and is captivated by Morwenna. Along with Caroline, Verity attends Valentine's christening where she unsuccessfully attempts reconciliation between the Warleggans and Ross. Both women are alarmed to hear their husband's ships are missing at sea, but Verity's spouse Andrew is found alive and well. Despite unexpected support from the Reverend Halse, Ross refuses to put himself forward as magistrate replacing the late Ray Penvenen, giving Warleggan the victory. Later Ross hears that Dwight has been cast ashore in revolutionary France and, with his friend Tholly Tregirls, sets out to rescue him.

Tholly takes Ross to a French port where republican soldiers are executing their prisoner. They meet Jacques Clisson, who gives them information about Dwight's incarceration but, threatened with prison himself, Ross returns home without his friend. Banned by Warleggan from using his church, the Carne boys find a venue for their Methodist meeting house, but are again thwarted by Warleggan through a legal loop-hole and are ultimately saved by Demelza, who allows them to use a barn on Ross's land. The Warleggans move to Truro, where even Elizabeth is shocked by the immoral social climbing of her newly appointed magistrate husband, and starts to feel isolated, but their absence leaves Morwenna, encouraged by Aunt Agatha and Geoffrey Charles, to continue meeting Drake.

Guests come to Ross and Demelza's daughter Cowance's christening. Morwenna and Geoffrey Charles are called away for Christmas. George plots to marry Morwenna off for political gain, but her heart belongs to Drake. Ross, Demelza, and Caroline find a way to feed the poor. Dwight continues to suffer in French prison.

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.

Whilst Ross returns home a hero and Morwenna and Drake continue to meet in secret Dwight, severely traumatized by his experiences, frightens Caroline by his seeming indifference to her. Ross brings Hugh Armitage who succeeds in helping Dwight get rid of his demons. Aware of the spirited Geoffrey Charles' loyalty to the clandestine lovers Warleggan arranges to send him to boarding school, but when Geoffrey Charles gives Drake a parting gift, Warleggan uses it to accuse Drake of theft. He is eventually released, and the heavy price for his acquittal is that Morwenna must marry Whitworth.

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.

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.

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.

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.

Ross and Demelza's domestic life is interrupted when a plea from Ross's old Army colonel compels him to London. Following Elizabeth's death, George's grief leads the Warleggans into uncharted territory.

As George makes a lucrative alliance, the Poldarks are caught in a deadly web...

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. Geoffrey Charles and Cecily's relationship continues to blossom, but George's sanity continues to deteriorate and Cary struggles under mounting responsibilities. The Enyses look to challenge the county's high society by hosting a ball to introduce the Despards, before disaster strikes and Ross and Ned must spring into action together.

Ross and Demelza are caught in the middle as Ralph Hanson tries to ruin Ned Despard and rebellion in Cornwall is stirred.

Ross tries to persuade the government to reinstate Ned as governor of Honduras, but Ned voices controversial views. The miners are distrusting of paper money. Morwenna visits John Conan. Demelza and Sam try to raise funds for a school.

Ned and Kitty face dire consequences and Ross attempts to help them. Cecily and Geoffrey Charles seek a life together against her father's wishes.

Demelza discovers the French are smuggling arms into Cornwall, but Ross is determined to take revenge on Merceron and Hanson for framing Ned and returns to London to confront them.

Ross and his friends must launch their most daring plan yet to try to save themselves and the country from enemies both at home and abroad.

Demelza discovers the French are smuggling arms into Cornwall, but Ross is determined to take revenge on Merceron and Hanson for framing Ned and returns to London to confront them.

Ross tries to persuade the government to reinstate Ned as governor of Honduras, but Ned voices controversial views. The miners are distrusting of paper money. Morwenna visits John Conan. Demelza and Sam try to raise funds for a school.

A cheerless Christmas looms for the Poldarks with Francis drowned in the mine having only found fool's copper and Ross facing debtor's prison if he cannot pay Warleggan. Ross is also anxious to expose the traitor and agrees to a dangerous scheme to trap them whilst Demelza is troubled by his frequent visits to console Elizabeth - though Warleggan is quick to ingratiate himself with the widow. Ray Penvenen accuses Dwight of fortune hunting and tries to ban him from seeing Caroline but she is far too perceptive and realistic to give up the man she loves. She also bails out Ross, whose tenacity she admires, in his hour of need - whilst seeking to remain anonymous.

The mine is at last bringing Ross wealth but Demelza, still slow to forgive, goes to stay with new mother Verity. An angry Ross gives the snide Warleggan a beating after his suggestion that Ross is cheating Elizabeth's son out of his inheritance before deciding to reenlist to fight in the Napoleonic wars. Dwight also signs up as a naval surgeon but is reunited with Caroline before he sets sail. Warleggan builds fences around his property, cutting off the public right of way and Demelza is one of the casualties of his hired thugs. Irate locals march on his house, Trenwith, vowing to burn it to the ground, but Ross dissuades them to spare them prosecution before he is reconciled with Demelza.

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.

An epidemic sweeps through the county and Dwight is grateful to Caroline for providing him with a cart-load of fresh oranges to combat it. Ross meanwhile is thwarted in his efforts to expand the mine, thanks to Warleggan and his proxy, Tankard. To provide finances he strikes a deal with a local smuggler to use his beach to land cargo on, much to Demelza's annoyance. Ross also goes into partnership with Francis, despite Warleggan's attempts to split them up, and they open up the mine gaining access to Wheal Grace. Demelza gives birth to a baby boy, Jeremy, which goes some way towards reconciling Francis with Verity.

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.

Ned and Kitty face dire consequences and Ross attempts to help them. Cecily and Geoffrey Charles seek a life together against her father's wishes.

Whilst anxious to build their own Methodist chapel, the Carne brothers work well at the mine, though they defy Ross by entering Warleggan's estate, where Drake meets and is captivated by Morwenna. Along with Caroline, Verity attends Valentine's christening where she unsuccessfully attempts reconciliation between the Warleggans and Ross. Both women are alarmed to hear their husband's ships are missing at sea, but Verity's spouse Andrew is found alive and well. Despite unexpected support from the Reverend Halse, Ross refuses to put himself forward as magistrate replacing the late Ray Penvenen, giving Warleggan the victory. Later Ross hears that Dwight has been cast ashore in revolutionary France and, with his friend Tholly Tregirls, sets out to rescue him.

Ross and his friends must launch their most daring plan yet to try to save themselves and the country from enemies both at home and abroad.