1919: Jack Ford returns to Gallowshields on Tyneside after service in the Great War. He befriends the Seaton family—parents Bill and Bella, and their children: attractive schoolteacher Jessie, Socialist medical student Billy, and black sheep Tom. Billy and Jessie try to involve Jack in the local Labour Party against the Liberal candidate and magistrate, former Major Pinner, who is against votes for women. Pinner not only wins, but makes himself unpopular by trying a shell-shocked war hero who got into a fight whilst confused and scared.

Billy, Tom and old army pal Matt try to involve Jack in the Labour movement but he seems uninterested. Bella takes in Harry, a young orphan. Father Keenley, the local priest, tells Bella that she could adopt but this would put a strain on resources and it might be better if she allows the boy to be sent on an emigration scheme to Australia.

Times are hard as the miners strike over a pay claim and Tom, now married with a son to keep as well as Mary, who has tuberculosis, borrows money from the seemingly flush Jack. Jack meets Matt's sister Dolly Mather, a war widow with whom he has an affair. Aware that Jack is involved in some sort of scam, Tom threatens to expose them unless Jack counts him in so Jack and Matt take Tom on their nocturnal 'fishing trip', in reality stealing sheep. They have a narrow escape after a run-in with a policeman but Jessie, against Jack's expectations, condones his activities.

Jack visits Sir Horatio Manners, father of his late commanding officer, to gift him a sword. Manners knows this is a ploy for Jack to ingratiate himself but is regardless impressed by his guile and offers him a job at his new factory, supervising non-union workers. This angers Jessie, who sees Jack as betraying his kind but they reconcile after Jack rescues Tom, in need of money and working as a 'black-leg', from being beaten up by his striking colleagues.

As the strike continues, Bill approaches an old friend, regarding the location of a mine shut down fifty years earlier. Tom pursues two children who have stolen leeks from his allotment but, on discovering that their mother is a war widow with no pension, makes a gift of leeks to them. Billy decides to quit his studies and, while Bill initially offers no opposition, he belittles the lad in the hopes that he will change his mind. The three Seaton men work on the shallow pit that Bill begins to dig under the floorboards — and eventually, Tom holds up a lump of coal in triumph.

The strike ends with no concessions won by the colliers. Jack triumphs at the factory and Manners suggests that he could do better than Jessie. Jessie goes on a date with the older, formal Arthur Ashton, who proposes, though she turns him down. Matt tells Jack that Dolly is pregnant and so he agrees to marry her. Bill, injured at the pit, is offered a payment by the mining company but at the expense of admitting his own liability. Jack bitterly opposes this and holds out for a better settlement, winning Jessie's admiration.

Encouraged by French onion seller Pierre, Bella turns the front of the house into a shop, using some of Bill's compensation. Bill, still bound to a wheelchair, is initially hostile but sees the need for income. Jessie is impressed by the intelligence of 14-year-old pupil Ronnie and tries to dissuade him from working in the mine but his mother is a widow and he wants to earn 'man's money'. He goes to work in the pit and is killed, causing Tom, who was looking after him, to quit. Jessie gets engaged to Ashton whilst Jack weds Dolly at the registry office.

Mary dies. Jack is in a pub when he meets old army colleague Sid Hepburn, still a professional soldier who suggests that Jack re-enlist as soldiers' pay is very good. Paddy Boyle, an Irish member of Jack's sheep-stealing gang, is convinced that Hepburn and his friend Bartram are the two British soldiers responsible for rape and murder back in Cork. Jack realises that Paddy is a member of Sinn Fein. Having considered Hepburn's offer, Jack declines rejoining the army but is too late to stop carnage when Bartram and Hepburn are shot by Paddy and his Sinn Fein comrade Lynch. Despite a warning cry from Jack, Paddy is also shot by a British soldier.

Nurse Rosie Trotter returns to Gallowshields and is mutually attracted to Tom, though, out of respect for Mary, they agree to postpone their nuptials for a year. Meanwhile, Bella's uncle Mick dies in hospital, having first placed a bet on a horse in Bella's name. To compensate for his funeral, Bella does cleaning work and is pleased to feel independent, which Bill resents. Mick's funeral is well-attended and the horse he backed won but unfortunately, the bet was never formally placed as the bookie was operating illegally.

Dolly is pregnant and Jack jobless so he agrees to a proposition from Manners, who wants to buy a house from Lord Calderbeck. Jack, posing as a parvenu car parts tycoon, will act as front man. At the house, he meets Freddy, Calderbeck's nephew and heir, though His Lordship resents him as he survived the war, unlike Calderbeck's sons. Freddy is suspicious of Jack but the merry widow Jane Cromer, Freddy's fiancée, is partial to a bit of rough and climbs into Jack's bed. Ultimately, Jack persuades her to marry Freddy and, thanks to inside information from Billy, working on His Lordship's land, gets a good sale for the house with a healthy commission for himself.

It is New Year's Eve and Glaswegian socialist lecturer Sandy Lewis joins Jack, whom he tells that the Labour Party is in the ascendancy, at the George Hotel, where Billy is bartending and Tom evades capture, having stolen from the cloakroom. They join Bill and Bella at a party given by Jessie and Ashton, to whom she is now married. The next day, the Seatons are summoned for allowing their shop to remain open in the evening. Bill suspects they were grassed up by rival shopkeeper Davidson.

To the annoyance of her husband, Jessie has been nominated for the Labour Party executive and Jack antagonises Dolly – who senses an ulterior motive in backing her. Jessie's nomination is successful. She has a bright pupil, Robert Armstrong, for whom she is seeking a scholarship and romance seems to be in the air between Matt and Robert's mother Lizzie. However, Lizzie is independent and rejects Matt after securing a well-paid cleaning job. Meanwhile, Tom is on the run, wanted for theft and illegal gambling, and Jack, having patched things up with Dolly, plans to help him escape to London.

Tom is caught and remanded. Jack becomes the deputy branch secretary of the union, getting the miners on side to dissuade them from strike action. The widow Downey – who actually informed on Tom – faces eviction as she is unable to pay the rent and is locked out by the landlord. When Jack and Tom appear in court, Tom is sentenced to three months' incarceration and Jack to one, but Jack is released to a hero's welcome.