The year is 1790 and there is riot and revolution in the air. Ross Poldark must fight for his freedom when George Warleggan tries to have him hanged as a revolutionary.
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.
As the election leads to rioting, Elizabeth goes to Bodmin herself. Demelza tries to influence the case by making a personal appeal to the judge, but George has a number of tricks up his sleeve as the day of the trial arrives.
Ross and Demelza face financial ruin, and George plans revenge on Jud. Francis, meanwhile, tries to rebuild his life and extends an invitation to Ross and Demelza.
Needing money to open a mine free of George's influence, Ross strikes a deal with a local smuggler. Dwight, meanwhile, tries to diagnose an epidemic and receives help from an anonymous benefactor.
An informant in the smuggling ring poses a serious threat to all. George buys Ross's debt to finally crush him. Caroline returns to Cornwall to make an announcement.
Ross tries to financially support Elizabeth in the wake of Francis's death, but George calls in Ross's debt. Demelza toils loyally to protect all at Nampara, and Dwight and Caroline continue to meet in secret.
Caroline convinces Dwight they must elope for a new life in Bat, as Ross sails with Trencrom to meet with Mark Daniel. Caroline is forced to pull her plan forward but it is threatened when Rosina dislocates her knee again. Dwight believes he can treat her and still rendezvous with Caroline; however, he and Demelza become suspicious that Charlie Kempthorne is the informant when they learn he has avoided the smuggling run. Dwight confronts Charlie, and a fight ensues. Demelza realises Ross will be walking into an ambush and attempts to warn the boat, but McNeil and his soldiers arrive at Nampara, leaving her under guard. Dwight incapacitates Charlie and escapes as Caroline sneaks out of Killewarren to meet him. Dwight attempts to warn Ross but is too late. Will Ross find a way to evade the soldiers? Having paid men to harass Trenwith with the aim of driving Elizabeth to him for protection, George arrives at her home and posts his men to guard Elizabeth, who is both shocked and grateful for George's attention. Dwight is released by the soldiers, but finds Caroline has already returned to London
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.
Demelza refuses to speak to Ross and expects him to return to Elizabeth, abandoning her and Jeremy. Elizabeth and Agatha believe the same and Elizabeth writes to George to postpone the wedding. George rides to Trenwith to make Elizabeth agree to another date, ensuring his plans are not usurped. In Truro, Tonkin invites Ross to join him in a prospering shipbuilding partnership. Meanwhile, Demelza accepts Sir Hugh Bodrugan’s invitation to his ball, where she finds Captain McNeil, inviting him to her room, having justified the possibility of adultery as something Ross has driven her to. Ross finds Demelza on Hendrawna Beach but hasn’t the words to build a bridge between them. Ross is beckoned to the mine where they have cleared the collapse and come upon the richest lode of tin Henshawe has ever seen - may Ross soon may be free of debt?
Elizabeth tells George that she is carrying his child and George continues to mark his territory by erecting fences around Trenwith, denying commoners passage across his property. Dwight learns of Caroline's new engagement and enlists in the navy. Ross decides he must mend the rift between Caroline and Dwight before it is too late. Ross is called to Trenwith by George, suspicious that the purchase of Geoffrey Charles' share in the mine was fraudulent. Pascoe reveals to Ross that George will seek to bankrupt him through court proceedings. Demelza is assaulted for trespassing on Warleggan land provoking the villagers to march on Trenwith with vengeance in mind - will Ross be able to disband the mob? Elizabeth, meanwhile, is forced to face the possibility that her pregnancy might not, in fact, be the result of her union with George.