Sixteen Tons

Voidwater, Nevada. 1873.
U.S. Marshal John Walker arrives in a frontier mining town to investigate five disappearances and a dead sheriff. What he finds is a company that won't answer questions, a darkness in the mine that doesn't behave like darkness should, and Bob Reynolds, a stable worker with shadows that move wrong near to him and also the most handsome man that John had ever seen.
The town calls Bob "the Sentry". John calls him beautiful, calls him Bobby in the dark above the stables, and doesn't ask about the things he sees that don't make sense until the night something comes out of the mine and Bob stops pretending to be just a stable boy.
There's an old darkness beneath the mountain. The O.X.E. Mining Company is drilling toward it anyway, and John Walker has a choice to make about what matters more.
Some doors shouldn't be opened. Some thresholds are better left alone. And some people are worth staying for, even when staying means watching the world end or standing beside the one thing keeping it from ending.