In O'Henry's short story, Bob is waiting for his friend, Jimmy Wells. This is a very special appointment because this appointment was made twenty years ago.
Accordingly, twenty years ago, both men made a promise to meet at the same time and place in New York City in order to confirm the rightness of their individual decisions. It appears that, at the time, Bob was determined to seek his fortune elsewhere, but Jimmy insisted on staying and working out his destiny in New York City. Each was equally persuaded that his own conviction was the right one.
They chose to meet after twenty years because both felt sure that this would be an adequate period for either man to carve out their own destiny and their own fortunes, 'whatever they were going to be.'
Bob tells the policeman that he is certain Jimmy would meet him because 'he always was the truest, stanchest old chap in the world.' He asserts that if his old friend turned up, it would be worth the thousand miles he had to travel to meet with him.
As is O'Henry's style, Jimmy does turn up, but Bob is in for the surprise of his life when his old friend sends another detective to arrest him. Even after twenty years, Jimmy recognizes his old friend, who is a wanted man in Chicago. Staying true to his humanity and to his duty as an officer of the law, Jimmy manages to capture a wanted criminal while preserving the memories of a shared camaraderie from years ago.