The turning point of a literary narrative is synonymous with the climax, or point of highest emotional intensity. Is it not ironical that the turning point of O. Henry's "The Last Leaf" conincides with the turning of the final leaf to yellow and dying? For, when old Behrman joins Sue upstairs in hers and Johnsy's flat, and they apprehensively stare out the window by Johnsy's bed, "the looked at each other for a moment without speaking."
This line is the turning point of O. Henry's short story because it is at this point that both Sue and Behrman have the emotional realization that Johnsy will give up her spirit if she sees that all the leaves have died on the outside vine. It is also at this moment that Behrman realizes that he must do something to save Johnsy. The little curmudgeon then decides to paint the leave onto the window in order to rescue Johnsy from certain death. This is his "masterpiece" as it is his gift of love for the young woman, a sacrificial gift as he dies, ironically, from pneumonia himself after having painted in the cold rain.