"You've put it very roughly, but I think I can see what you are driving at," returned Forrester.
"Continue the idea a little further, Mr. Forrester," went on Humphrey. "If you were making a mine survey you would first lay out your boundaries, tunnels and so on, on the surface, wouldn't you?"
Forrester nodded.
"Then you would carry those lines below the surface. In other words, the lines you had laid out on the surface would be a guide to you when you got below it."
Again Forrester nodded.
"All right," said Humphrey. "I think you've got my idea about this case, and what I mean by solving it by triangulation. You will take the people, and the events which have occurred, and use them as your prominent landmarks; that is, points for your triangles. You will then study what lies between those landmarks, and also what lies under the surface. By that means I think you will eventually discover some clues that will be worth while.
"For example; take Mr. Nevins, who was the last victim of the 'Friends of the Poor,' as the first point of your triangle. Take his bank as the second, and his home as the third point. Instead of measuring the distance between these points by feet or rods, measure it by people and events. Set down, just as you would the figures of a survey, the names of his friends and acquaintances, the men with whom he has done business, and any little out-of-the-way events which have taken place in his life, so far as you can ascertain them. Do this with the other people who have been concerned in the blackmailing activities of this band. By arranging your triangles so they will overlap if possible, you will get at a starting point. Somewhere the lines will cross, and at the point of intersection a definite clue may form."
"Mr. Humphrey," laughed Forrester, "you are giving me a man's-size job."
"I know it!" admitted Humphrey. "But the man who solves this case has got to put more than ordinary brains and ability into it. You have got to forget the old rules and theories and formulas. That is why the experienced detectives are falling down. They can't forget the rules! When you suggested a while ago that you thought of turning detective, I immediately saw its possibilities. Your engineering training has taught you how to study cause and effect, and work out plans for meeting unusual conditions. You start with a mind trained to solve difficult problems, but at the same time your mind is free of all the traditions of the detective craft. Things they wouldn't notice, or consider important if they did, will impress themselves upon you and start a train of thought.
"Now then," exclaimed Humphrey, jumping to his feet, "I have over-stayed my welcome and I must get back to the office and write up my story for tomorrow's paper. You can rest assured, however, that the important details of this conversation will not get into print until you say the word. But remember, when the big scoop comes—it belongs to me!"