Title: The mantle of silence
Description: This antique 1920's book takes place in Canada and has been one of my favorites since I read it as a teen in a log cabin in Maine.
Lots of canoeing and wilderness exploration, but with a huge mystery to be solved about the strange uncommunicative young woman who hires a guide to carry her gear into a secret place weeks into the uncharted forested chains of lakes. 
The mystery deepens as the woman blindfolds the young male guide for a portion near her secret destination (hidden gold mine) deep in the Canadian wilds. Then tragedy strikes and the young woman becomes comatose. He takes care of her as she suffers from complete amnesia when she awakes as another person with another identity entirely. The young man is trapped in an unfamiliar place weeks away from any civilization...That is only one of the mysteries