In this short story, the bounty hunter Ben Price is hot on the heels of Jimmy Valentine(alias Ralph Spencer), a small-time bank robber and specialist in safe-cracking. Since his release from prison, several "jobs" have been done with Jimmy's "signature" on them, namely his expertise and opening the vaults. But Jimmy can't be nabbed as there is no real proof against him.
As Jimmy plans his next hoist, he meets the banker's daughter and falls in love. He decides to "go straight" and open a local shoe store and lead a decent life. One day when he is visiting his future father-in-law at the bank, two little girls are playing and one locks up the other in the vault. As the vault is time-set and will not open until the next day, Jimmy recuperates his burglary tool box and opens the vault so the little girl will not suffocate.
This is just the incriminating evidence Ben Price has been waiting for, but instead of arresting Jimmy (who hands himself over to be taken in), he pretends he doesn't even recognize him. Price realises that Jimmy is now reformed from his gangster ways and decides to give him a second chance.
In this light, both men are "heroes" since each has made a choice against self-interest: Jimmy Valentine, to save a little girl even if it meant going to prison again; and Ben Price, to give up a handsome bounty reward and to sacrifice his own reputation by giving Jimmy a fresh start. Of course, the stakes are higher for Valentine, but Price acts in everyone's best interest as well.
Note that O. Henry "did time" in jail too for bank fraud, and it was because of his prolonged confinement that he took up writing. Below are some notes on O. Henry's writing style and a biographical sketch of this intriguing personality.