Jimmy seems determined to become an honest man, but he is going to have a lot of explaining to do if he still hopes to marry Annabel and remain in Elmore. She and her whole family, including her father the banker, have seen that Jimmy is an expert safecracker and owns a set of state-of-the-art burglar tools. His only hope is to tell Annabel the truth, the whole truth, and nothing but the truth.
O. Henry does not explain what happens after Ben Price declines to arrest him and addresses him as Mr. Spencer. That seems to take care of Jimmy's immediate problem, but he still has to go back and face his fiancee and her entire family, who must be experiencing all sorts of conflicting emotions. If Ben Price could overlook Jimmy's past sins, then maybe Annabel would do the same. O. Henry specifies that she adores Jimmy.
To a woman nothing seems quite impossible to the powers of the man she worships.
“Can't you do something, Ralph—try, won't you?”
This would help his case a great deal. And the entire family would be forever grateful for his saving the life of tiny Agatha, who would surely have perished inside that bank vault if Jimmy hadn't made such a noble sacrifice by revealing his tools and his expertise.
Even if Jimmy went to prison and lost Annabel, he probably would have still remained an honest man for the remainder of his life. In his letter to his old pal Billy, he makes it clear that he has become a changed man.
It's the only life, Billy—the straight one. I wouldn't touch a dollar of another man's money now for a million.
Jimmy Valentine eventually becomes an honest man. After being pardoned from prison for safecracking, Jimmy Valentine immediately returns to safecracking as a career. It is inferred that he cracked safes in Richmond (a town in Indiana), Logansport, and Jefferson City. However, his life as safecracker abuptly ends when he meets Annabel Adams, the daughter of the local banker in Elmore, Arkansas. Instead of robbing the bank, Valentine opens a shoe store and goes legitimate. Ben Price, the investiger hotly pursuing Valentine, appears in Elmore to see him crack one last safe - not for money - but to save the life Annabel's niece Agatha who is trapped inside and will die if he doesn't help. Ben Price pretends not to recognize Valentine.