The flashback in this sinister and disturbing short story provides many details that should make the alert reader sit up and predict a terrifying ending for poor Mrs. Drover. Notice the almost ghostly way in which her fiance is described in the flashback - she seems to almost doubt his existence:
The young girl talking to the soldier in the garden had not ever completely seen his face. It was dark; they were saying goodbye under a tree. Now and then - for it felt, from not seeing him at this intense moment, as though she had never seen him at all - she verified his presence for these few moments longer by putting out a hand, which he each time pressed, without very much kindness, and painfully, on to one of the breast buttons of his uniform.
Note how the younger Mrs. Drover seems to need to check that he is still there, he is so ethereal and shadow-like. Also note how the man responds to these "checks" and his lack of empathy and the pain he inflicts on her - this surely indicates his ability to cause her more pain in the future. This is surely indicated when the narrator comments:
That cut of the button on the palm of her hand was, principally, what she was to carry away.
The pain and scar of this wound seems to symbolise there relationship. The ghostly comparisons continue as the girl imagines "spectral glitters" in place of her fiance's eyes and his lack of emotion and sensitivity and his refusal to embrace or kiss her reinforce his complete lack of care or concern for her.
Then, finally, note how the dialogue introduces another chillingly spooky threat. The man tells her that he is going "not so far as [she] thinks" and then his final speech expresses his promise which is uttered more like a warning:
"I shall be with you," he said, "sooner or later. You won't forget that. You need do nothing but wait."
All of these points indicate and foreshadow the terrible ending of this story where Mrs. Drover and her first fiance are reunited and he keeps his promise.