He was standing now with his back turned towards me, pulling his hand-
bag out of the rack. He had a furtive back--the back of a man who, in
his day, had borne many an alias. To this day I am ashamed that I did
not spring up and pinion him, there and then. Had I possessed one
ounce of physical courage, I should have done so. A coward, I let slip
the opportunity. I thought of the communication-cord, but how could I
move to it? He would be too quick for me. He would be very angry with
me. I would sit quite still and wait. Every moment was a long reprieve
to me now. Something might intervene to save me. There might be a
collision on the line. Perhaps he was a quite harmless man...I caught
his eyes, and shuddered...

His bag was open on his knees. His right hand was groping in it.
(Thank Heaven he had not pulled the hood over the lamp!) I saw him
pull out something--a limp thing, made of black cloth, not unlike the
thing which a dentist places over your mouth when laughing-gas is to
be administered. `Laughing-gas, no laughing matter'--the irrelevant
and idiotic embryo of a pun dangled itself for an instant in my brain.
What other horrible thing would come out of the bag? Perhaps some
gleaming instrument?... He closed the bag with a snap, laid it beside
him. He took off his top-hat, laid that beside him. I was surprised (I
know not why) to see that he was bald. There was a gleaming high light
on his bald, round head. The limp, black thing was a cap, which he
slowly adjusted with both hands, drawing it down over the brow and
behind the ears. It seemed to me as though he were, after all, hooding
the lamp; in my feverish fancy the compartment grew darker when the
orb of his head was hidden. The shadow of another simile for his
action came surging up... He had put on the cap so gravely, so
judicially. Yes, that was it: he had assumed the black cap, that