French saw that Macdonald, at least if he was a man of strong character, could give a lot of trouble. He would admit that he kept letters for Whitman, but would state that Whitman always called for these and that he did not know where his client was to be found. And the closest watch kept by the police might be quite unavailing. French remembered a case in point in the East End. Here a small newsagent had been chosen as the intermediary, and though the place was kept under observation for several weeks, the criminal was never seen. It was only when he was captured through an entirely different line of research that the reason came out. The newsagent had guessed his establishment was being shadowed and he had exhibited a prearranged sign. He had placed a certain article in a certain place in his window. The criminal, riding past in a bus, had seen the danger signal and had kept away. In the present instance French wished if possible to avoid the chance of a similar expensive and irritating delay. If he could devise some other method of attack, this clue of the tobacconist could be kept as a last resource. He took his problem home with him that night, and after he had dined he drew an arm-chair up to the fire and settled down comfortably with his pipe to think the thing out. For a considerable time he pondered, then at last he thought he saw his way. He worked at the details of his plan until he was satisfied with them, then with a smile of triumph on his lips and deep satisfaction in his heart he knocked the ashes out of his pipe, switched off the lights and went up to bed. CHAPTER NINETEEN The Last Lap Next morning Inspector French was early occupied in making the necessary preparations for his great _coup_. The first of these involved a visit to Messrs. Dashwood and Munce, and the business day had scarcely begun when he presented himself once more at their office. “I am sorry, Mr. Dashwood, for troubling you so soon again,” he apologised, “but I want to ask you one other question. Can you tell me whether Mr. Whitman saw your partner during his call? In other words, if Mr. Whitman were to meet Mr. Munce, would he recognise him?” Mr. Dashwood raised his eyebrows, but he answered without hesitation. “Mr. Whitman was shown in to me, and so far as I know, he did not meet my partner. But Mr. Munce is in his room. We can ask him.” The junior partner was a more good-natured looking man than Mr. Dashwood, and French was sorry he had not had to deal with him throughout. “No, I didn’t see him,” he said with a pleasant smile. “As a matter of fact I was out at the time you mention. I went over——” he looked at Dashwood—“to see Troughton about eleven and I did not get back till after lunch.” French nodded.