Sheriff Charlie Koch is preparing to go out for the day when his wife Ella wakes up. She wonders what time it is but Charlie says that his watch has stopped and it's pitch black out. The Sheriff figures that it's early in the morning. His prisoner Jagger is to be executed at 9:30 a.m. and he's disgusted that people will be turning up to watch. He tells Ella to bring Jagger his last meal.
At the sheriff's office, his deputy, Pierce, notes that it's 7:30 in the morning but it it's still night out. Colbey, the newspaper editor, comes in and admits that he's received dozens of call from people wondering what's going on. Some think that it's the end of the world. He admits he doesn't know and Charlie notes daytime should have come two hours ago. Colbey called the state capital and only their town is in darkness. When Colbey wonders what Charlie thinks of Jagger's innocence, the sheriff insists it was up to a jury. Pierce is more than satisfied, but Colbey points out that the dead man was a cross-burning bigot and Pierce perjured himself, testifying he saw Jagger shoot the victim from across the room. The dead man had powder burns on it, indicating the possibility of self-defense. Charlie didn't point it out, and Colbey didn't cover it in the newspaper.
Colbey goes in to see Jagger and explains what is happening outside. Jagger isn't interested and admits he has no friend or family. Depressed, he claims he'd rather kill himself but doesn't have the guts for it. Colbey asks him for a statement on his guilt or innocence and Jagger admits he's guilty. He once cared, taking up unpopular causes, but ended up considered the town kook. Jagger ended up taking on the town bigot but everyone in town respected the man.
The clock strikes 9 and it's still pitch-black out. The townspeople gather for the execution in a half hour and listen to the radio as the news talks of the strange phenomena. Charlie and Pierce arrive and Charlie wonders who or what is causing the darkness. As the time of execution approaches, Colbey wonders if they're going to go ahead and Pierce insists there's no reason not to. He snaps at Colbey, pointing out he's a lousy small-town newspaper editor and he won't put up with his accusation of perjury. Charlie admits that Colbey was right and he covered up the powder burns. A committee of townspeople told him there wouldn't be any autopsy and Charlie agreed so he could be re-elected. Colbey kept quiet so he could sell newspapers, and Pierce wanted to feel important. Pierce grabs him, angry, but Charlie tells him to drop it.
The two law officers go to get Jagger and bring him to the scaffold. Reverend Anderson, a black man, admits that Jagger stood up for him and his kind and asks if he wants to make a final statement and find some peace. Jagger refuses and sneers at the crowd, which are eager to see him hang. He refuses to say that he's sorry and Anderson tells him not to dishonor himself. He asks if Jagger had regrets when he shot the man and Jagger boasts that he enjoyed killing the victim. Anderson finally admits that he realizes Jagger is guilty and it's a good thing to be with the majority.
Charlie and Pierce execute Jagger as the crowd looks on. Anderson wonders if any of them, including himself, have learned anything or seen past their hate. He tells them that the blackness closing in is the hate that they all felt, and there's so much that they've cast it out and it's rising up. The darkness grows ever stronger, blotting everything out.
In the sheriff's office, Charlie, Pierce, and Colbey listen to the radio as the news reports that the darkness is spreading over everyplace where hate can be found. And the lights grow dim…