Dark Places by Jon Evans

In a place so harsh that survivalis a struggle, one man has found the strength to kill ...

Paul Wood is a modern vagabond, a man who chooses to leave the comforts of San Francisco to spend months backpacking through some of the world's most challenging terrain: Cameroon, Indonesia, Nepal. While hiking in the Himalayas, Paul gets more of a rush than he bargained for when he finds the body of a murdered hiker, the victim mutilated in a way that Paul has witnessed once before, years ago and thousands of miles away.

To quell a scandal, the police rule the death a suicide and close the case. But Paul can't let it go. A man who has traveled through the thin air at the top of the world and across land mines in war zones, he is not easily discouraged. But his newest expedition will show him some of the darkest places imaginable, in both the terrain he navigates and the men he encounters. Finding the killer becomes Paul's new obsession -- a journey that leads him dangerously close to the edge ... and maybe over it.
 
- Goodreads Summary