A Pattern of Islands discussion

I never questioned the credibility of the narrative of the author - the highly logical and practical Arthur Grimble - so when he describes walking south along the eastern beach path in the northern tip of the most northerly of the Gilbert Islands, and passes a limping man walking north along the same path who fails to respond to Arthur's greeting, and that turns out to be, according to the evidence Arthur presents, the spirit of a guy who had just died a bit further south, then how can i NOT begin to think WHAT???? And the author doesn't even analyse the whole thing for the reader's sake. What's your views on this?