Aubert's news told me that our Hun antagonists must have some very big plan in hand. Even the most desperate of spies draws the line at murder, unless he finds himself in an impasse with no other way out. This is not, of course, from any special reluctance to taking the life of an enemy, but simply as a matter of self-preservation. For we are so peculiarly constituted that we tolerate calmly the work of pestiferous agents whose activities are a greater peril to the community than a dozen murders would be, while the killing of a single man brings a hornets' nest about the murderer's ears. I knew therefore, that since the Huns had gone so far as to "remove" Gartin, they must be engaged in work of supreme importance, and must have been quite aware that he was hot on their trail. Truly we had an interesting prospect before us. But we were all tolerably well used to danger, and I do not think it affected any of us. "Only last night," said Aubert, "Cauvin entertained Bonnier, of the Admiralty, and no doubt he learned something from him. I have found out that he has been lending Bonnier a good deal of money. Bonnier has recently got mixed up with a fast set, and he has been spending a great deal more money than his income warrants. When people of that kind begin to consort with rogues of Cauvin's stamp it usually means only one thing." "No doubt that is true enough," I replied; "but for the present we must take even the risk of leaving Bonnier alone. I want absolute evidence that Cauvin's money comes from Germany, even though he actually gets it from a secret source in England. It is not enough for me to prove either that Bonnier is selling secrets or that Cauvin is buying them. I want to prove that Cauvin's money is German, and I am going to do it. Bonnier can wait; if we get Cauvin we are tolerably sure to obtain sufficient evidence to lay Bonnier by the heels at any time. In fact, we can remove him quietly as soon as Cauvin is out of the way. I shall leave for England to-morrow." This I did, and twenty-four hours later I was in London. I decided first to investigate Cauvin's supposed motor invention, and made my way to the office of a well-known patent agent in Chancery Lane. He had done some business before for me and greeted me warmly. I knew him so thoroughly that I did not hesitate to tell him exactly what I was after. "But, my dear Sant," he said, "if this supposed invention is being kept as a secret to stagger the motoring world, it is not likely to have been patented yet by either Cauvin or anyone else. Depend upon it, if there is anything in it, it is being manufactured secretly, and will not be patented until it is absolutely ready for the market. To patent it now would simply be setting every motor expert in the country at work on similar lines. You know the patent lists are watched with the keenest scrutiny. My clerk is looking into the matter, and we shall soon know whether Cauvin has patented anything."