All the next day, which was Sunday, the problem of the magneto remained subconsciously in French’s mind, and when on Monday morning he took his place in the 10.30 A.M. Limited to return to Devonshire, he was still pondering it. In a dream he watched the bustle of departure on the platform, the arrival of more and ever more travellers, the appropriation of seats, the disposal of luggage. (That armature _had_ been tampered with. It must have been, because otherwise it would not have worked in with a prearranged crime.) Lord! What a pile of luggage for one woman to travel with! American, he betted. (But, it could not have been done at the time. In no way could it have been made to fail just when it was wanted.) What price that for a natty suit? Why, the man was a moving chessboard! What was the connection between chessboard suits and horses? (It must have been tampered with; but it couldn’t have been. That was the confounded problem.) There was the guard with his green flag, looking critically up and down and glancing first at his watch and then over his shoulder at the platform clock. It was just twenty-nine and a half minutes past. In another half minute. . . . Suddenly into French’s mind flashed an idea and he sat for a moment motionless, as with a sort of trembling eagerness he considered it. Why, his problem was no problem at all! There was a solution of the simplest and most obvious kind! How had he been stupid enough not to have seen it? As the guard waved his flag French sprang to his feet, and, amid the execrations of the porters, he hurled himself and his baggage from the moving train. Then, smiling pleasantly at the exasperated officials, he hurried from the station, jumped into a taxi, and told the man to drive to the Ardlo Magneto Works in Queen Elizabeth Street. “Sorry to trouble you so soon again, Mr. Illingworth,” he apologised on being shown in, “but I’ve thought of a way in which that car could have been disabled at the time and place required and I want to know if it will hold water.” “If your method covers all the factors in the case as you have described it, I should like to hear it, Mr. French.” “Well, it’s simple enough, if it’s nothing else. I take it that if the magneto of my car goes wrong I can buy another?” “Why of course! But I don’t follow you.” “They are all made to a standard—interchangeable?” Mr. Illingworth whistled. “Gee! I’m beginning to get you! Yes, they’re all made standard. There are several models, you understand, but all the magnetos of any given model are interchangeable.” “Good! Now tell me, what’s to prevent my man from buying a duplicate magneto, damaging the armature winding invisibly with a needle, and running it on his car till it gives up; then taking it off, carrying it as a spare, and putting it on again when he had got the car to the point of breakdown?” “You’ve got it, Mr. French! Great, that is! I didn’t think it was possible, and there, as you say, it’s as simple as A B C.”