What story did the man standing near the hardware store tell the passing cop?

The man standing outside "a darkened shop" explains to the cop why he is there. He says that he is waiting for a friend—the two of them agreed twenty years earlier that they would meet here on this particular night. He explains that there was once a restaurant here, where he had dinner with his best friend, Jimmy Wells. The two of them grew up together in New York "like two brothers," and Jimmy loved the city so much that he would never have left. The waiting man, however, moved out to the West. The two agreed that they would meet in this place in twenty years to see what had become of each other. The man has come a thousand miles to meet his friend tonight. He says he was successful in the West and is intrigued to see what has become of his friend.
Ultimately, the twist in the tale is that the cop is Jimmy Wells—he recognizes his old friend as a man wanted by Chicago police. Instead of giving himself away, or arresting the man himself, he "went and got another cop and sent him to do the job."