Ben Price is Jimmy's equal. Jimmy is an expert at cracking safes; Ben Price, an expert at catching safecrackers. Ben shows his expertise in part of his dialogue:
"Look at that combination knob—jerked out as easy as pulling up a radish in wet weather. He's got the only clamps that can do it. And look how clean those tumblers were punched out! Jimmy never has to drill but one hole."
These were the days before the federal government took over most of the work of protecting banks. Ben Price likely works for one of the big private detective agencies which banks employed for protection. Ben is obviously a specialist in banks and knows a lot about Jimmy Valentine's methods and criminal exploits. He has already arrested Jimmy Valentine once and sent him to prison for four years for a bank job in Springfield.
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.
Although Price is probably not a police detective, he has certain powers as a private detective. He can make citizens' arrests and turn culprits over to the official police. He can provide the district attorney with evidence to convict them. Once he gets on Jimmy's trail, he is relentless.
“That's Dandy Jim Valentine's autograph. He's resumed business. Yes, I guess I want Mr. Valentine. He'll do his bit next time without any short-time or clemency foolishness.”
Ben Price's dialogue marks him as Jimmy's nemesis. It may be partly for fear of the detective that Jimmy moves all the way to Arkansas and tries to set up a shoe business as a front behind which he can continue to operate as a safecracker in his new territory. He doesn't expect to fall in love.
Price easily traces Jimmy to Elmore, Arkansas, and is prepared to arrest him for the four bank jobs he pulled right after being released from prison. Jimmy's decision to use his tools to rescue the little girl trapped in the bank vault, induces Ben Price to forgive Jimmy's past offenses. As a private detective, Ben is not obliged to make an arrest if he decides against it.
“Hello, Ben!” said Jimmy, still with his strange smile. “Got around at last, have you? Well, let's go. I don't know that it makes much difference, now.”
And then Ben Price acted rather strangely.
“Guess you're mistaken, Mr. Spencer,” he said. “Don't believe I recognize you. Your buggy's waiting for you, ain't it?”
By personifying Ben Price as the sole representative of all the forces of justice in the country, O. Henry makes his story a dramatic conflict between two unique individuals: Jimmy Valentine, the master criminal, and Ben Price, the master detective.