forgotten past
It seems that in this movie, Burt Lancaster's character, Neddy, has forgotten who he once was. It is though he abandoned his family, friends and lovers a couple years ago and recently suffered a bout of amnesia. Although he can remember everybody he meets, he seems to have forgotten the damage he has done to those that cared about him. He slowly descends into a sort of madness when the realization of who he once was begins to deepen, and he is left with the aftermath.
Also, notice that the movie starts on a beautiful mid-summer day and ends on an inclement, fall afternoon with fallen leaves on the ground. This sort of goes with the changing mood of the film.