I have recently been reading a collection of Christie short stories including the one with the above title, which is about a treasure hunt on the Isle of Man that was used to promote its tourism industry. Were the clues ever explained ? By googling "daily dispatch isle of man 1930" (the story having been serialised in that paper that year) I discovered 3 of the 4 rough locations, 2 of which I had already guessed based on clues in the story not available to the characters in it. I also believe I know the remaining rough location. But what I'd like to know is how the clues available to the characters enabled them to pinpoint the locations.