Carrados smoked thoughtfully, his open, sightless eyes merely appearing to be set in a tranquil gaze across the room.
"It would not be an improbable explanation," he said presently. "Ninety-nine men out of a hundred would say: 'People do not do these things.' But you and I, who have in our different ways studied criminology, know that they sometimes do, or else there would be no curious crimes. What have you done on that line?"
To anyone who could see, Mr. Carlyle's expression conveyed an answer.
"You are behind the scenes, Max. What was there for me to do? Still I must do something for my money. Well, I have had a very close inquiry made confidentially among the men. There might be a whisper of one of them knowing more than had come out—a man restrained by friendship, or enmity, or even grade jealousy. Nothing came of that. Then there was the remote chance that some private person had noticed the signal without attaching any importance to it then, one who would be able to identify it still by something associated with the time. I went over the line myself. Opposite the signal the line on one side is shut in by a high blank wall; on the other side are houses, but coming below the butt-end of a scullery the signal does not happen to be visible from any road or from any window."
"My poor Louis!" said Carrados, in friendly ridicule. "You were at the end of your tether?"
"I was," admitted Carlyle. "And now that you know the sort of job it is I don't suppose that you are keen on wasting your time over it."
"That would hardly be fair, would it?" said Carrados reasonably. "No, Louis, I will take over your honest old driver and your greasy young signalman and your fatal signal that cannot be seen from anywhere."
"But it is an important point for you to remember, Max, that although the signal cannot be seen from the box, if the mechanism had gone wrong, or anyone tampered with the arm, the automatic indicator would at once have told Mead that the green light was showing. Oh, I have gone very thoroughly into the technical points, I assure you."
"I must do so too," commented Mr. Carrados gravely.
"For that matter, if there is anything you want to know, I dare say that I can tell you," suggested his visitor. "It might save your time."