The short story "A Retrieved Reformation" fulfills all that defines O. Henry's stories. For one thing, it has the signature surprise ending of this author: Just as the reader believes that Jimmy Valentine is about to be arrested, he receives his "retrieved" reformation as his pursuer, the detective Ben Price tells him that he is mistaken in identifying him:
"Guess you're mistaken, Mr. Spencer,....Don't believe I recognize you. Your buggy's waiting for you, ain't it?"
Along with the other surprises of the story such as the appearance of Ben Price and Agatha's being locked into the bank vault, there are such characteristic traits in O. Henry's story such as the little ironies that frequent the tale, and the tone of gentle humor and sentimentality. For instance, Jimmy Valentine leaves prison with no intention of not robbing banks, but when he comes to Elmore, Arkansas, where, ironically, he falls in love with the daughter of the town's bank president. Wishing to now remain in this town, Jimmy becomes a respectable shoe story owner and courts Annabel Adams. In an effort to put his past behind him, Jimmy writes an old crony, offering his kit of tools. On the day in which he is going to take these tools on the train, Annabel wants him to see the new vault in the Elmore Bank. While there, holding his kit, one of the little girls of the family locks another in the vault. Mr. Adams is frantic because the combination has not yet been set. So, ironically, Jimmy Valentine saves the girl with his burglary tools.
Regarding O. Henry's sentimentality, Valentine's criminal nature is miraculously transformed by his falling in love with Annabel Adams. Ben Price, the detective who has long pursued Valentine is so moved by Jimmy's rescue of Agatha and sacrificing of his safety, that he believes him reformed enought to let go.
And, with respect to O. Henry's gentle humor, after Jimmy arrives at the hotel where his burglary kit is still hidden, he later goes down to the lobby:
"Got anything going on?" asked Mike Dolan, genially.
"Me?" said Jimmy, in a puzzled tone. "I don't understand. I'm representing the New York Amalgamated Short Snap Biscuit Cracker and Frazzled Wheat Company."
This statement delighted Mike to such an extent that Jimmy had to take a seltzer-and-milk on the spot. He never touched "hard" drinks.
In addition to the characteristics of surprise ending, irony, sentimentality, and gentle humor, there is one more that is also typical of O. Henry: the "moral of the story." At the end Jimmy Valentine proves what the warden has observed at the beginning: he is "not a bad fellow at heart."