Ben Price is the detective who successfully has arrested Jimmy Valentine and secured his conviction and prison sentence.
As the primary investigator of the Jimmy Valentine case, Ben Price has come to understand the strategies and modus operandi of Jimmy Valentine. That is, he knows the methods and skills of the safe breaker and robber; also, he understands the workings of Valentine's mind, as well.
After Valentine is released from prison and returns to his crimes, Ben Price investigates the scenes of these robberies and remarks, "That's Dandy Jim Valentine's autograph. He's resumed business....Yes, I guess I want Mr. Valentine." Having learned the habits of this robber, Ben again goes on the trail for "Dandy Jim." When the trail leads him to Elmore, Arkansas, where a new safe has been installed in the local bank, Price positions himself within this bank, waiting for his prey.
However, when he witnesses Valentine's sacrifice of his new persona because of the obvious love he has for the banker's daughter, Annabel Adams, romantically taking the rose she wears and placing it in his vestpocket, and proceeding to pull out his safe-cracking tools, Price realizes that Valentine now has truly "reformed." So, when Valentine is halted as he tries to leave the building and submissively says, "Well let's go. I don't know that it makes much difference, now," Price "acted rather strangely." For, Price, who has come to know Jimmy Valentine very well realizes that this man is truly changed. Feeling that he deserves a "retrieved reformation," Price feigns lack of recognition, and he allows Ralph Spencer to depart on his own.
Price is, then, the agent of O. Henry's exploitation of the romantic notion that people are essentially good and unselfish, especially when motivated by the love of another.