Northern England. Connolly, shop steward at the Martindales factory, meets Travers, a union agitator from London. Travers warns that their relationship must remain secret.

Shopfloor worker Tom Curtis tells colleague and lodger Joe of his financial worries now that his wife, Anna, is pregnant again. Teddy boy Barrett and his gang discuss whether to attend the forthcoming union meeting. Introduced to new employee Travers, Connolly pretends not to know him. Following a near accident with a lathe, Connolly complains about the absence of safety guards; works manager Davis replies that the workers take them off themselves.

At home, Tom discovers the TV isn't working. Tom apologises to Anna for his earlier mood, and reassures her that he does want the baby. Joe goes out with Pat, who he has been pursuing for weeks. She tells him she knows his reputation, and that she's not like his other girls. He becomes annoyed.

Connolly and Travers talks tactics before the big union meeting. The works committee proposes an unofficial strike if demands are not met. Despite complaints that the action has no official backing, the motion is carried. Later, Tom gets frustrated with Joe's indifference. When the strike inevitably begins, Tom and a few others risk their colleagues' wrath by crossing the picket line. That night, they become victims of an intimidation campaign: windows are smashed, washing lines cut, rubbish emptied. Later, Connolly warns Barrett to cool it down. Nevertheless, the violence escalates. Rattled, the dissenters give in. But a row with Connolly makes Tom change his mind.

Mr Martindale tells the board that the strike must end before it endangers a big government contract, and suggests a compromise package. To Connolly's surprise, Travers tells him to back the offer, and mentions a plan to deal with Tom's insubordination. Next day, with the strike over, Tom finds his colleagues - even Joe - are ignoring him. Late that night, Tom, uncomfortably, passes on a request that Tom to stand down as manager of the factory football team. Anna rails at Joe for his disloyalty, saying she wants him to move out.

Tom's story is picked up by the local paper, then by national press and television. The story further enflames opinion against Tom. Martindale tells Davis to sack Tom if necessary to avoid losing the contract. But, irritated with Connolly, Davis refuses to bow to his demands. He tries to persuade Tom to apologise; Tom refuses. Later, with Anna, he agonises over what to do.

One day, Cathy returns home without her brother, Brian. Frantically, Anna rushes to the school, finally finding Brian weeping in the toilets; he has been covered in paint by bigger boys. When Tom goes to him, Brian calls him a 'dirty scab'. In the canteen next day, Tom snaps, telling his colleagues to leave his family alone. Later, Pat confronts Joe, begging him to do something. Joe shrugs it off.

Travers tells his London associates that they can use Tom's outburst to call the men out again, sabotaging Martindales' contract. Connolly tells Davis his members are working to rule until Tom is sacked. When Davis responds that he could as easily sack him on the same basis, Connolly puts it about that management are threatening sackings, prompting another walk out. Martindale summons an official union representative.

Next day, with police help, Tom forces his way through the angry picket line. Barrett eyes him threateningly. That night, Pat tells Joe that Tom has been hurt. He heads to the hospital, where he learns that Tom has lost an eye in a hit and run. He was speaking the name 'Gladys' - nickname of one of Barrett's gang. On his motorbike, Joe tracks down Barrett and Gladys. Terrified, Gladys insists Barrett was responsible. Joe corners Barrett, and, despite Barrett's knife, overpowers him. He drags him back to the factory, where the union representative, trying to persuade the workers to abandon the strike, is being shouted down. Reluctantly, Joe takes the microphone, and tells them about Tom's 'accident', expressing his shame that he and they let it happen. The crowd listens in silence. Finally, Joe stands down and makes his way through the crowd; Pat follows. Travers takes the train back to London.