Ben Price is Jimmy Valentine's nemesis. Ben is a tough, experienced, intelligent detective. O. Henry does not say that he is a police detective. Ben seems to be the kind of detective who worked for big private agencies like the famous Pinkerton National Detective Agency, founded in 1850. In O. Henry's day the federal government was not involved in protecting banks. Bankers had to hire their own security services. It wasn't until the U.S. Congress passed legislation creating federally guaranteed protection of bank deposits that the government got involved in protecting the banks through the FBI. Those were the days of famous gangsters like John Dillinger, Bonnie and Clyde, and Pretty Boy Floyd.
When Jimmy Valentine gets out of prison he goes to the rented room that has been kept for him by his pal Mike Dolan, who owns the building and runs the cafe on the ground floor.
He got his key and went upstairs, unlocking the door of a room at the rear. Everything was just as he had left it. There on the floor was still Ben Price's collar-button that had been torn from that eminent detective's shirt-band when they had overpowered Jimmy to arrest him.
It was Ben Price who arrested Jimmy and got him sent to prison for the "Springfield job" ten months or so earlier. When Jimmy gets his specially designed tools out of their hiding place, he commits three safecracking jobs in banks in Indiana. Naturally the banks call for help from the agencies they employ for protection.
The losses were now high enough to bring the matter up into Ben Price's class of work. By comparing notes, a remarkable similarity in the methods of the burglaries was noticed. Ben Price investigated the scenes of the robberies, and was heard to remark: “That's Dandy Jim Valentine's autograph. He's resumed business.
By this time Jimmy has decided that he is getting too well known in the area. He decides to move to a different territory of operations. He chooses the town of Elmore in Arkansas and opens a shoe business as a "front," an occupation that will make him look like a respectable citizen. He also changes his name to Ralph Spencer. Quite unexpectedly, he falls in love at first sight with Annabel Adams, and he decides to go straight because he knows she would never have anything to do with a criminal. Furthermore, he finds that he is prospering in the shoe business and that he enjoys the straight life.
But Ben Price, his nemesis, traces him to Elmore and is waiting in the bank to arrest him for the three bank jobs he pulled in Indiana. When Jimmy feels compelled to open his suitcase and use his incriminating burglar tools to open the bank vault where the hysterical little girl has been accidentally trapped inside, he has to reveal the fact that he is a professional safecracker. It looks as if his reformation is destroyed. He will lose his beautiful fiancee, his business, and his new identity. He knows Ben is waiting for him and that he will get a heavy prison sentence. But Ben has been impressed by Jimmy's noble sacrifice. In one of O. Henry's famous surprise endings, Ben tells Jimmy:
“Guess you're mistaken, Mr. Spencer,” he said. “Don't believe I recognize you. Your buggy's waiting for you, ain't it?”
So Jimmy''s reformation is miraculously "retrieved." No doubt he will have a lot of explaining to do to Annabel and her father, but they will forgive him because of his heroic action and because, like Ben Price, they will feel assured that Jimmy is thoroughly and truly reformed.