Then one day, for no reason he could give, though the reason felt familiar, he stopped climbing up the airshaft to peek at Helen, and he was honest in the store."
The quote is made toward the end of the final chapter of the book, Chapter Ten. Frank has completely taken over Morris Bober's store. He works hard and all day long—first running the store and then acting as a counter—boy all night long in order to supplement the measly earnings of the shop. One day, in his fatigue, he becomes despondent. He has been working so hard because of his love of Helen, but when one no notices and she continues to see Nat Pearl, he feels distressed. In his distress, dishonest behaviors resurface. He starts cheating his customers slightly, and he starts sneaking into the dumbwaiter to spy on Helen. But then one day, for no clear reason he suddenly stops again and fully starts to be honest again, as this quote makes clear. Frank's return to honesty, as noted in this quote, shows his final conquest over his less honorable behaviors. While he had sought to control his innate dishonesty throughout the text, now his goodness seems innate and over his final attempts as dishonest actions it triumphs without Frank forcibly willing it to be so.