The climax, the most intense part of a story,is the turning point because it determines the outcome of the main conflict. The most important struggle Gurov has is within himself. He easily attracts other womenbut doesn't respect them. When he first meets Anna, he just wants a casual fling. He knows from "really bitter experience" how complicated an affair can be. He keeps this cool attitude toward the affair until he returns home to Moscow. Then he realizes he can't forget about her and goes to her town to find her. It is at this point when he realizes he is no longerthe type of man who can have a casual affair with a woman. Anna has changed him into a responsibleman who no longer feels women are "the inferior race". The two of them truly love each other.
A turning point might be in part 3 when Gurov leaves his home and goes to find Anna in her provincial village. This is when Gurov's obsession finally leads to action on his part, and where we learn more about his character.