The Hike by Lucy Clarke

Four old friends with a shared past set out on a hiking trip in the Norwegian wilderness. They cross towering mountains, glass-like lakes, log cabins and forests that seem stolen from a fairytale. When a broken body is found at the bottom of a ravine, it becomes clear someone knows exactly why the woman has died, and in this remote landscape there is a killer on the trail.

Purchase from Bookshop.org