It will naturally be supposed that this side-line leading to the sand-pit is going to provide the explanation, the quite simple explanation of the disappearance of the express. But if the matter had been as simple as the side-line would appear to make it, I should hardly have omitted it from the first map. I could have said at once: "It is quite clear that, owing to a train of circumstances which it remains to determine, the express, instead of continuing to follow the line B A, must have turned off up the side-line H I, and buried itself in the vast mass of loose sand at the sand-pit I. Rushing along at a speed of over sixty miles an hour, it evidently plunged into the mass of sand, which covered it up; and that is the stupid but actual reason of its disappearance." But, to say nothing of the fact that this does not explain the presence, at the point D, of the guard's-van and railway-carriage, out of the window of which Signor Petito had stuck his head, this explanation could not have failed to occur to the alert intelligence of the engineers of the company. Moreover, there were points and a switch at the point H; this switch, in accordance with the rules, was padlocked; and the key had been taken away. I indeed attached no importance to the fact that _the padlock was locked_; for, it seemed to me quite probable that the key had been left in the padlock, _which had actually been the case_, and that Theophrastus, who had good reasons for stopping the train in order to join Signor Petito, had profited by the presence of that key, to shift the points. It was only a matter of thrusting over the lever of the switch; and that would explain why the train was not seen by the signal-man at A, since, instead of continuing along the line B A, it had turned off up H I towards the sand-pit. I told myself all this; and if it had explained anything, I should have stated it at once, and instead of giving two maps I should have given merely the latter with the side-line H I on it. That I have not done so is owing to the fact that the side-line H I explains nothing. I also believed at first that it was going to make the disappearance of the express clear to us, but as a matter of fact _it complicates the catastrophe instead of explaining it_; for here is the story, the true story; and that too continues to explain nothing at all.