Ross Poldark decides to join the army to avoid charges of smuggling and leaves behind Elizabeth. When he returns three years later, he finds his father dead and his estate in ruins and his sweetheart engaged to somebody else. He takes on a new kitchen maid after rescuing her from a beating and is soon in conflict with hostile locals.
After the local mine Wheal Reath is closed, a huge amount of miners, including Jim, find themselves out of work. Ross offers Jim the job as a farm-hand, and thinks to resurrect his family's mine with the hope of bringing prosperity to the region once again.
Elizabeth has a baby and Ross attempts to put on a brave face at the christening, where he is furious to hear people talking about his relationship with Demelza. Wheal Leisure mine opens and the miners immediately hit ironstone, requiring extra money for gunpowder.
Ross and Demelza's marriage shocks Trenwith with Charles' amusement at the union causing a fatal heart attack. On his death-bed he asks Ross to look after Francis for him. Verity visits Nampara and despite Demelza's concerns that she is too common for her the two quickly become good friends.
Ross and Demelza welcome a couple of new arrivals as Dwight Enys a doctor who plans to make a study of lung diseases at Wheal Leisure shows up and their baby daughter, Julia Grace Poldark is born. At Julia's christening, Demelza decides to try and lift Verity's spirits by getting her back together with her with her lost love Captain Blamey.
The Carnmore smelting company is a success and Ross makes more of an enemy of George by outbidding him for copper at auction. Meanwhile, Francis is increasingly volatile now that he has lost his mine and is reduced to working the land, so Verity avoids speaking to him about her plans to marry Captain Blamey.
When Ross and Zacky discover there is fever at Bodmin Jail just weeks before Jim is to be released, Ross asks Dwight to accompany him to the prison. Ross forces his way into the jail and discovers that Jim is near death. They break Jim out from the jail in a desperate attempt to save him.
Returning home, Ross is expected to attend George's grand ball. He is sickened at the thought of going amongst the people responsible for Jim's incarceration, but Verity persuades him that he must do it for Demelza and Julia's sake; to remind everyone that he is one of their class so they won't arrest him for the prison break. However, at the ball Ross is fighting drunk and Demelza is aghast that she has been left to fend for herself at her first ever high society social event.
Ross finds it hard to keep the Carnmore smelting company going and George Warleggan is determined to see it close down. George's agents outbid Carnmore so that it has no copper and George attempts to talk its shareholders, who all remain secret except Ross. Following a rockfall at Wheal Leisure Mark returns home early and discovers that Keren is not there. He finds her at Dwight's house and learns that they have been sleeping together.
Ross attempts to turn around the fortunes of Carnmore one last time but afterhe is outbid he reluctantly shuts the company down. George takes the opportunity to rub his face in it. Feeling guilty about Keren's death, Dwight immerses himself into work, dealing with an outbreak of the putrid throat. Ross finds out that all at Trenwith are stricken with the disease and he attempts to persuade Dwight to treat them. Demelza attempts to help and becomes infected and passes it on to baby Julia.