Ross Poldark returns from fighting in the American Revolution to his native Cornwall, finding his fiancée Elizabeth Chynoweth about to marry his wealthy cousin Francis and his home in ruins after his father's death. Ross is a reluctant wedding guest, along with George Warleggan, nephew of a prosperous banker, and his uncle Charles proposes financing him to move to London. Ross, however, stays in Cornwall, rebuilding his home. Whilst at the local market he rescues the waif-like Demelza Carne and takes her home to work for him. Her bullying father arrives with his sons to reclaim her but Ross's tenants turn up to help him and fight them off.

Ross decides to reopen the family copper mine Wheal Leisure and persuades Francis to help him. Ross also escorts Francis's put-upon sister Verity to a dance, where he crosses swords with George Warleggan, annoyed that Ross borrowed capital for the mining project from a rival bank to that of his uncle. Verity meets the sea captain Andrew Blamey, who is keen to marry her but George forbids it, claiming that Blamey killed his first wife. The relationship ends when Francis challenges Blamey to a duel, in which Francis is injured, though Demelza proves her worth when she tends to him, impressing Ross.

Ross reopens Wheal Leisure, drawing his work force from Charles' mine and winning the respect of his tenants. Whilst he and Demelza are at a local wedding Elizabeth gives birth to a son, Geoffrey Charles. Ross attends the christening , noting not only the growing friendship between George Warleggan and Francis but overhearing gossips speculate on his relationship with Demelza. He is genuinely impressed by her efficiency and starts to confide in her. One of his workers, young father Jim Carter, is taken to court for poaching and Ross speaks on his behalf but fails to prevent the boy being sent to prison. Drunk and miserable he returns home and ends up in bed with the comforting Demelza. Next day he is visited by a sympathetic Elizabeth, clearly unhappy in her marriage. Seeing them together Demelza prepares to leave but Ross urges her to stay and they get married.

The news of Demelza and Poldark's marriage spreads through the community, threatening Wheal Leisure's prospects.

Wedding bells ring as miner Mark Daniel marries visiting actress Keren Smith whilst Demelza and Ross have their own celebration as their daughter Julia is born, Ross not allowing Demelza's father's unwelcome visit to the christening party to ruin matters. Young Dr Dwight Enys comes to the area and is befriended by Ross. He is progressive and philanthropic, which annoys the curmudgeonly incumbent Dr Choake. With widespread poverty and mine closures all around Ross proposes that the pit owners form a collective with their own smelting company, to beat the Warleggans' monopoly, and presses ahead with the scheme. Francis opts out and is subsequently ruined as his mine is forced to close. To repay Verity for her kindness Demelza reunites her with Andrew Blamey in town, where they witness a food riot by starving locals.

Whilst Ross's cooperative has some success there are hard times throughout Cornwall and typhoid sweeps through Bodmin jail and kills Jim Carter just as Ross and Dwight break in to rescue him. Dwight is also called upon to visit the injured Keren, who throws herself shamelessly at the young doctor, as Demelza notices. Untouched by privation the Warleggans throw a ball where Francis, struggling to accept his reduced circumstances, neglects Elizabeth, allowing George to step in as her escort. Ross turns up drunk and confronts Halse, the magistrate who jailed Jim and then plays cards recklessly though he does expose his opponent as a card sharp, known to the Warleggans, who are now all the more determined to break him. Further scandal is caused by the arrival of Captain Blamey, who asks Verity to run away with him.

Francis wrongly blames Ross for helping Verity elope with Andrew Blamey. Meanwhile, Mark suspects Dwight and Keren of having an affair, starting chain of events which will have tragic consequences and threaten the safety of eveyone in Nampara.

Ross faces ruin as, along with the rest of his collective, he must sell to the Warleggans' company at a nominal price. At the same time the disease known as putrid throat sweeps through the county, claiming many lives and Dwight, still contrite over Keren, throws himself into trying to treat it. Elizabeth and her family are stricken and Demelza goes to help them but infects herself and her daughter with disastrous results. Divine justice appears to intervene as the Warleggans' ship and its cargo founder on the rocks and Ross leads the villagers in collecting its spoils from the beach. Demelza recovers from her sickness, only to face another setback to her marriage.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.