Based on a true story and Harry R. Irving's play Bohunk, a coal miner is manipulated into becoming a strike leader.
Coal miner Joe Radek (Paul Muni) walks to work but would rather see Anna Novak (Karen Morley) than go to a meeting. Steve Croner (J. Carrol Naish) complains they aren't paid for dead work and criticizes the union. Mike Shemanski (John Qualen) argues, but Joe prevents a fight. Joe drives Anna and her family to a dance. Joe invites policeman Slim (William Gargan) to his wedding. Anna tells Slim they must inform Joe, but Slim is going to Pittsburgh. Anna asks Slim to take her. Joe learns that Anna left with Slim and gets drunk. At the union meeting official John Farrell (Joseph Crehan) warns them not to form a new union; but Joe supports Croner, who reports the trouble to Jenkins (Purnell Pratt) and McGee (Barton MacLane). Croner tells Joe to be a big shot. Joe and those without a union button are not allowed to work. Joe leads men to disrupt the work. J. W. Hendricks (Henry O'Neill) gets a letter from Jenkins offering strike breakers. Croner gets Joe elected strike leader and president of the new union. Mike disagrees with Joe, and Sophie Shemanski (Sara Haden) tells Joe he must leave Mike's house.
The mine is closed but Hendricks hires new men from Jenkins and McGee, who outfits police. Workers are offered worse conditions. Jim learns that Croner is gone, and they see scabs going into the mine. McGee's police on horses clear strikers from the streets. Strikers are evicted for not paying rent, and one spits at Joe. Mike fights a cop to protect a woman and is beat up by McGee. Joe fights and is beat up too, but Mike is killed by McGee. In the hospital Joe asks Sophie why they killed Mike. Anna comes back to her family and visits Joe. At a meeting men want to go back to work. Joe steals food, and Anna sees him take explosives. Joe says he won't let anyone work so they can win. Anna helps him, and Joe asks her to tell them he won't let anyone in. Joe explodes the mine. Anna tells Welsh (Willard Robertson) that Joe is in there. Welsh calls Joe. McGee shoots tear-gas, but Joe calls Welsh he will destroy the mine. Anna calls Joe they are coming in the back. Joe stops all but McGee with an explosion. McGee shoots at Joe, who jumps him and keeps him hostage without food. After several days an investigation reveals the racketeers' manipulation to make money supplying strike-breakers. Anna goes in to tell Joe he did it. McGee is arrested for murdering Mike. Joe and Anna are cheered and will raise kids.
This drama reflects increased union activity in the midst of the Depression. In 1934 dissidents from the AF of L formed the CIO and elected United Mine Worker president John L. Lewis chairman. However, this film warns that workers can be led astray by greedy manipulators.