This looked like a snag, but French reminded himself that at the moment he was only getting information and his theorising could wait till later. He continued his questions, but without learning much more. “Now, Gurney,” he said at last, “under no circumstances are you to mention what we have been speaking of—not to your wife nor to Mr. Fogden nor to anyone. You understand?” “I understand, sir, right enough.” “Very good. Now I’m anxious to go into this matter further, and I’ll call at the works to-night.” “Right, sir. I’ll be on the lookout.” It was dark as French rang at the big gate of the works. Gurney soon appeared at the wicket and French followed him across the yard to the boiler-house, a distance of perhaps forty yards. It was a fair-sized shed, housing five Babcock & Wilcox water-tube boilers with mechanical stokers and the usual stoker engines and pumps. On a ledge of the warm brickwork near one of the ash openings stood the old man’s can of tea, and his basket of food was placed on the repair bench close by. French took in these details and then said: “I want now to try an experiment. Will you lend me your key of the wicket. I will go out, lock the wicket behind me, and go round to the office door and ring. When you hear the ring you go and open. Repeat everything exactly as you did that night so as to get back here at the same time. In the meantime I shall let myself in again by the wicket and see if I should have time to dope your tea and get away again before you appear. You understand?” This program was carried out. French went out and rang at the office door, then ran round to the large gate, let himself in through the wicket, found the can of tea, opened it and counted ten, closed it and relocked the wicket. Then he began to time. Three minutes passed before Gurney appeared. So that was all right. Anyone who had access to the key in the office could have doctored the watchman’s food. Moreover, the fact that the Gurneys had breakfasted without ill effect on the remainder was not such a difficulty as French had at first supposed. The criminal might have doped the tea on his first visit and during his second poured away what was over and replaced it with fresh. In fact, if he were to preserve his secret he must have done so. The discovery of the drugging would have started an enquiry which might have brought to light the whole plot.