In that scene when Caleb (Chris Pine) and John Loomis (Chiwetel Ejiofor) look into each other's eyes, with Caleb hanging precariously over the edge of the cliff, I felt pretty certain that Loomis would pull him to safety. In the subsequent scene, when Loomis tells Ann (Margot Robbie) that Caleb departed for Anson, I was convinced that Loomis released his grip and allowed Caleb to fall to his death. The perfectly ambiguous nature of the ending reminded me a lot of the way "Angels With Dirty Faces" ended, in which you had to decide as the viewer whether Cagney's character went out like a yellow rat or at the request of Father Jerry. I imagine most viewers for this film would take the position that Loomis's jealousy over Caleb's appearance caused him to seek the latter outcome I mentioned, but the alternative at least has a degree of credibility if you want to stretch for it. However the shattered, silent gaze between Ann and John to close out the story is probably all you need to know to confirm the more violent outcome.
The mystery the film could have answered more definitively was what the heck the title was supposed to mean. In keeping with a recurring reference to Ann's religious upbringing, a child's Biblical book titled 'A is For Adam' is briefly shown, so one might consider 'Z for Zachariah' to bookend the picture's suggestion of the first and last man on Earth. It probably should have been done in a more coherent manner, as I was more perplexed by the title than what happened to Caleb.
The mystery the film could have answered more definitively was what the heck the title was supposed to mean. In keeping with a recurring reference to Ann's religious upbringing, a child's Biblical book titled 'A is For Adam' is briefly shown, so one might consider 'Z for Zachariah' to bookend the picture's suggestion of the first and last man on Earth. It probably should have been done in a more coherent manner, as I was more perplexed by the title than what happened to Caleb.