The Great Depression
The Great Depression was ironic to many people, but especially to William, who had just uprooted his life and gone West, hoping for a brighter tomorrow. Instead of finding work, he learns that no one has any jobs, because the economy has stalled. The Depression hits him hard, because it came to him during a season of transition, so he has absolutely nothing to fall back on, and no home to return to. The Depression makes him into a hard-working, but still homeless, man.
Salvation to a coal mine
William Music just wants an honest job where he can make some money. That's what he was looking for when he headed West. Then, when the Great Depression strikes, and he finds himself truly destitute, it takes a savior to bring him out of homelessness. Ella Bone offers him a way out of abject poverty, but it is not an easy gig. He must work in the coal mines during a season of hostility and instability.
The union's ironic victory
The union doesn't have enough traction to be a threat until paranoia brings dysfunctional tendencies out in the company. The company resists the union politically, but after work gets more and more hostile, they switch over. The ironic victory of the union comes when the union's threats exacerbate the dysfunction in the mines. By threatening to strike, the union gains something worth striking about. Communist or not, the workers have to agree that being forced to work at gunpoint is absurd.
The self-defeating leader
Hardcastle owns the coal mine, so he can do what he wants with his employees, he feels. When all of a sudden, a Communist union starts gaining traction in the town, threatening to strike against unfair labor practices, he has a decision to make. Should he be political and try to meet some demands, or should he play hardball? His name implies his answer. Ironically, his commitment to fear tactics destroys the company he worked hard to build.
Violence and desperation
When Hardcastle decides to take things a step further, requiring his mine guards to carry rifles, his desperation is clear. What isn't clear to him is that obviously violence will destroy the social fabric tying this coal town together. The desperation on both sides makes tensions soar, and when guns get introduced, that is a sad and ironic failure in the town. Instead of being a community that supports one another, they have been driven to violence.