On the morning of an execution in a small town, Sheriff Charlie Koch prepares to go to the station to prepare for the killing. His wife Ella wakes up and wonders what time it is and why it’s so dark out. Sheriff Koch tells her its early morning but his watch stopped and he isn’t sure exactly what time it is. Complaining that he hopes no one shows up, he tells Ella to bring the condemned man his last breakfast.
At the station, Deputy Pierce wonders why it’s still dark out despite the fact it’s 7:30 a.m. in the morning. The local newspaper editor, Colbey, comes in and confirms that people have noticed the darkness and some are wondering if it’s the end of the world. He's checked with the state capital and confirmed that only their small town is shrouded in darkness. They discuss Jagger's trial and Sheriff Koch insists that it was the jury's decision. Pierce, a blatant bigot, is happy Jagger's going to be killed. Colbey points out that the dead man was a bigot and that Pierce claimed Jagger shot him from across the room. He accuses Pierce of perjuring himself, noting there were powder burns on the dead man's shirt that would have shown Jagger acted in self-defense. However, Colbey and Sheriff Koch both covered it up as well.
Colbey talks to Jagger who could care less about the darkness. He considers killing himself but admits he's too much of a coward. Colbey asks Jagger if he wants to confess and the prisoner admits that he was guilty. Once an idealist, he took up unpopular causes and fought back against bigotry, including the man he killed. All it got him was a reputation as the town kook, and now a death sentence.
It's 9 o'clock, a half hour before Jagger's execution. The people stare out into the darkness and wonder what's happening. Sheriff Koch and Deputy Pierce arrive to check the gallows and Colbey wonders if they're going to continue with the execution. Pierce doesn't see any reason not to and Colbey continues to needle him. Pierce snaps, saying that Colbey is just a small-town newspaper editor and he's no better than Pierce. Sheriff Koch admits that Colbey is right and he covered up the evidence that might have cleared Jagger's name. He wanted to be re-elected, Pierce wanted to be a hero, and Colbey wanted to sell papers.
As Koch and Pierce go to get Jagger, Colbey discusses the case with Reverend Anderson. Anderson, a black man, admits that Jagger didn't want to see him or receive any spiritual assurances. Koch and Pierce arrive with Jagger. Anderson wonders if he wants to make a final statement and find some measure of peace, noting he's accused of killing a bigot on behalf of Anderson and the other African-Americans in town. Jagger, unimpressed, sneers at the crowd and boasts that he's guilty. Even Anderson has to admit that Jagger did what he was convicted of. As Jagger ascends the stairs, he accuses Anderson of joining the majority in hate and Anderson says that the minority died 2,00 years ago.
Koch and Pierce execute Jagger and Anderson wonders if any of them can see past the hate. He gives them his theory of what's going on: they've all been so consumed by hate that it has spilled out and is covering the world in darkness. As their hate grows, the world grows darker and darker still.
Later, Koch, Pierce, and Colbey listen to the radio. News broadcasters are announcing that new areas of darkness are appearing across the world: over Dallas, over ghettos, over political prison camps, over anywhere that hate can be found.