He had not lied when he said her statement had impressed him. That it represented her firm conviction he had not the least doubt. And it certainly was a point in Berlyn’s favour that such testimony should be forthcoming from his wife, when it was evident that their married life had been an indifferent success. Of course it might be simply that the woman did not wish to be involved in the misery and disgrace which would come with proof of Berlyn’s guilt. But French did not think it was this. Her thought had seemed to be for her husband rather than herself. It was still fairly early in the afternoon and French thought he would have time to make another call. He therefore walked up the Fulham Road and took an eastbound district train at South Kensington. Half an hour later he was at the headquarters of the Ardlo Magneto Company in Queen Elizabeth Street. When the managing director heard French’s business he touched a bell. “You had better see Mr. Illingworth, our chief electrical engineer,” he said. “I am afraid I could not help you in these technical matters.” Mr. Illingworth was a pleasant young man with a quiet, efficient manner. He took French to his office, supplied him with cigarettes, and asked what he could do for him. French put his problem, recounting the enquiries he had already made. “Those people told you quite correctly,” was Mr. Illingworth’s answer. “Your question is this: Could a man drive a car up to a certain place and then short circuit the magneto armature so that the car couldn’t be started again? The answer is, Yes, but not without leaving marks.” “But that’s just my puzzle,” French returned. “That’s exactly what seems to have been done.” “Well,” Mr. Illingworth answered with a smile, “you may take it from me that it wasn’t.” “Then in the case that I have described, the breakdown must have been a pure accident?” “I should say, absolutely. Mind you, I don’t say that a breakdown couldn’t be faked without leaving traces. It could be. But not so as to stop the car then and there. The concealed injury would take time to develop.” “That’s a bit cryptic, isn’t it? Can you make it clearer to a lay intelligence?” “Well, it is possible to damage the insulation by jamming a needle into the armature winding between the wire and the iron core, and if you’re careful it’ll leave no mark. But it won’t disable the magneto straight away. In fact, the car will run as usual and it may be a considerable time before any defect shows. But sparking takes place at the injury, perhaps at first only when the engine is working specially hard. This causes carbonisation of the insulation, leading eventually to complete breakdown. The car begins to misfire and it gradually grows worse until it won’t run at all.” “I follow you. I may take it, then, that it is possible to cause a breakdown without leaving a mark, but that this is a comparatively lengthy process and cannot be done at a given time.” “That’s right.”