From Mountaineer to... Assassin?

I won't lie, when I first read the plot synopsis for this novel, I questioned how it would fit in with the likes of Annapurna and Into Thin Air (other than the obvious- that he does get sent to the Eiger). I was weary of how mountaineering would mix with a spy/assassination plot. Of course, from the beginning of the novel, the narration explains that Hemlock was a mountaineer before he worked for CII, so I wondered if that was going to be the only connection. Trevanian provides us with a neat and tidy answer to our constant question of "why climb?" by making Hemlock's trip to the Eiger a job- a sanction which will earn him 100,000 dollars. However, it cannot be that simple. As has been pointed out, this is a fiction novel, not a memoir. Trevanian chose to make Hemlock a mountaineer turned assassin (at least, when he needs the money), chose to make this “the Eiger Sanction” rather than placing the action somewhere else. For me this raised the question: why? Why was Hemlock a mountaineer turned spy? Why will the action of the novel  occur on the Eiger, “that treacherous face” (99)? These are questions we have not yet had to consider in the expedition memoirs we have encountered so far, but I think they are imperative to answer with this text. Also, the consideration these questions led me to wonder: how, if at all, does a spy/assassination/conspiracy theory novel set on a mountain help us answer the question “what do mountains do”?