Seeing the Light
The overriding irony of the story is that the protagonist must go down into the darkness in order to see the light. During his stay underground, Fred Daniels comes to learn things about himself and, especially, some ugly truth about the world above that he would probably never have learned otherwise.
Lawson
The name of the police officer who first beats a confession out of Fred and then shoots him to death is ironic on a couple of levels. One way of looking at his name is as an ironic undermining of the idea that law enforcement agents are the “sons of the law.” Another way is to consider how this man functions as the ideal that the “law is on” the side of providing justice for all.
Jewel Thieves
Fred steals from the jewelry store vault, but it is Thompson, the innocent night watchman who pays the price, first by beaten by the cops and then by killing himself. The even more striking irony, of course, is that an employee in the store is also stealing, yet goes unpunished.
Jewels
Another irony related to the theft of the jewelry store is that Fred doesn’t even steal them for their economic value. One of the lights he’s seen by going down into the sewer is the misplaced value that is placed on accumulation and acquisition in the capitalist world above. By contrast, the jewels are mere décor; a way to adorn and lend some beauty to the ugliness of dark world below.
“You’ve got to shoot his kind. They’d wreck things.”
The most particularly vicious irony in the story is related to officer Lawson’s justification to the other cops of his killing Fred. Lawson’s statement derives from a combination of deep-seated racism, intoxication with unrestricted authority and being a central element in a corrupt system. All those things collude to make his justification obviously meaningless to anybody but fellow cogs in the system. The vicious irony lies in the fact that despite the absence of any moral foundation to his assertion, he actually is telling the truth. Had Fred been able to communicate what he learned during his time in the sewer, he would have wrecked at least that tiny part of the systemic corruption related to those things he witnessed.
