Here was our first clue on the case. Many policemen work on theory so determinedly that they exclude really important facts which do not fit comfortably into the theory. I have always believed in taking the evidence, building a theory upon it, and then trying to confirm or reject that theory as new facts appear. It was well that we followed such a policy here, for we had nothing but the bomb-tube itself to build our theory upon. What did it offer? First, we were fortunate in having a bomb to study, for usually the fire following an explosion leaves no trace of its origin. We had its construction and ingredients as real, if vague, clues. Second, we knew that the _Kirkoswald_ had carried supplies to France, and that all of the vessels on which bombs had been found or fires had broken out, had also been carrying supplies to the Allies. The list, by this time, had grown, for there were three more ship cases of fires or bombs in May, one in June, and five in July. Our primary theory was, therefore, that the bombs were made and placed on the vessels either by Germans or their paid agents. [Illustration: _Copyright, by Underwood and Underwood, N. Y._ Lieut. Robert Fay (on right) and Lieut. George D. Barnitz after Fay’s arrest] [Illustration: _Copyright, by Underwood and Underwood_ From left to right: Fay, Daeche and Scholz, arraigned in Court] The _Kirkoswald_ carried sugar. By examining the cargo-records of the other ships which had suffered near or actual mishaps, we found that they had also carried sugar, and that in the instances when fire broke out, the highly inflammable sugar gave a lot of trouble to the fire crew. The vigilance of the waterfront and harbor police had of course been keyed up to detect anything suspicious, but a bomb-planter does not often carry his bomb under a policeman’s nose, and it seemed not unreasonable to suspect that the bombs had gone aboard with the sugar. So I went to a sugar refinery to see how sugar was made. I followed the process from the entry of the raw sugar to the bagging and shipping of the finished product. All of the sugar shipped abroad went in bags, which were sewn tight either by hand or by machinery. After considerable testing I found that it was fairly easy to open a hand-sewn bag and sew it up again without leaving evidence of what I had done; the machine stitches, however, resisted any intrusion, and were hard to duplicate once they had been taken out. I put that fact away for future reference and looked in on the shipping department, to learn there that the only two persons who could know of the destination of a consignment of sugar before it was actually loaded into a vessel’s hold were the shipping clerk of the refinery and the captain of the lighter who took the sugar from the refinery to the ship.