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