hear of it; he seems
to have taken a dislike to the signalman from the first, and latterly
he had forbidden him to come to his house or his daughter to speak to
him."

"Excellent, Louis," cried Carrados in great delight. "We shall clear
your man in a blaze of red and green lights yet and hang the glib,
'greasy' signalman from his own signal-post."

"It is a significant fact, seriously?"

"It is absolutely convincing."

"It may have been a slip, a mental lapse on Mead's part which he
discovered the moment it was too late, and then, being too cowardly to
admit his fault, and having so much at stake, he took care to make
detection impossible. It may have been that, but my idea is rather
that probably it was neither quite pure accident nor pure design. I
can imagine Mead meanly pluming himself over the fact that the life of
this man who stands in his way, and whom he must cordially dislike,
lies in his power. I can imagine the idea becoming an obsession as he
dwells on it. A dozen times with his hand on the lever he lets his
mind explore the possibilities of a moment's defection. Then one day
he pulls the signal off in sheer bravado--and hastily puts it at
danger again. He may have done it once or he may have done it oftener
before he was caught in a fatal moment of irresolution. The chances
are about even that the engine-driver would be killed. In any case he
would be disgraced, for it is easier on the face of it to believe that
a man might run past a danger signal in absentmindedness, without
noticing it, than that a man should pull off a signal and replace it
without being conscious of his actions."

"The fireman was killed. Does your theory involve the certainty of the
fireman being killed, Louis?"

"No," said Carlyle. "The fireman is a difficulty, but looking at it
from Mead's point of view--whether he has been guilty of an error or a
crime--it resolves itself into this: First, the fireman may be killed.
Second, he may not notice the signal at all. Third, in any case he
will loyally corroborate his driver and the good old jury will
discount that."

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 t