Tess' killing of Alec is perhaps the most puzzling part of the novel. Readers can't help but think that if Tess had simply walked away from Alec and could've lived long and happily with Angel. If Tess felt Alec would be a continuing danger to her marriage, she surely knew that killing Alec meant her marriage would only last a few days and her life would end in about a month.
Professor James Heffernan, an English literature scholar, thinks he has the answer. He says that Alec had taken possession of Tess' soul and finding the need to break that possession, Tess believed nothing short of killing him would work.
Heffernan's answer is put forward here to generate comments. Do you agree with Heffernan that at the time of her cohabitation with Alec he possessed Tess' soul? If you disagree, do you think Tess' soul was still her own and was it likely to remain so?
I have my own opinion to share if we can get some interest on this thread.