This impressive short story by Margaret Atwood contains one central mystery that is explored and resolved through the flashback of Lois to the loss of her childhood friend, Lucy, in the Canadian wilderness. The strange and mysterious disappearance of Lucy in the wilderness, with no signs of her remains ever being found, is something that impacts Lois profoundly in the rest of her life. Note what we are told towards the end of the story as we return to the adult Lois:
She was tired a lot, as if she was living not one life but two: her own, and another, shadowy life that hovered around her and would not let itself be realised--the life of what would have happened if Lucy had not stepped sideways, and disappeared from time.
This experience has affected her so much that after Lucy's disappearance she never wanted to go "to any place with wild lakes and wild trees and the calls of loons." However, in spite of this deliberate avoidance of the wilderness, within herself she is always listening for some kind of "echo," presumably referring to the voice of Lucy. It is only at the end of the story that she reconciles her loss of Lucy and the wilderness that is within her by finding Lucy in each of the paintings that hang on her wall:
Everyone has to be somewhere, and this is where Lucy is. Sheis in Lois's apartment, in the holes that open inwards on the wall, not like windows but like doors. She is here. She is entirely alive.
Thus the mystery of the text is resolved, as by finding Lucy in each of her paintings Lois acknowledges the importance of the wilderness in her own life and is able to reconcile herself to both the loss of Lucy and the wilderness element that exists within her.