locking and
unlocking of compartment doors, one of the small T-shaped kind that you
can buy of almost any iron-monger for sixpence or a shilling any day. It
was wet from contact with the snow, but quite unrusted, showing that it
had not been lying there long, and it needed but a glance to reveal the
fact that it was brand new and of recent purchase.

Cleek held it out on his palm as he climbed back upon the car and
rejoined Narkom.

"Wherever he got on, Mr. Narkom, here is where the murderer got off, you
see, and either dropped or flung away this key when he had relocked the
compartment after him," he said. "And yet, as you see, there is not a
footstep, beyond those I have myself just made, to be discovered
anywhere. From the position in which this key was lying, one thing is
certain, however: our man got out on the opposite side from the platform
toward which the train was hastening and in the middle of the right of
way."

"What a mad idea! If there had been a main line express passing at the
time the fellow ran the risk of being cut to pieces. None of them slow
down before they prepare to make their first stop at East Croydon, and
about this spot they would be going like the wind."

"Yes," said Cleek, looking fixedly at the shining bit of metal on his
palm; "going like the wind. And the suction would be enormous between
two speeding trains. A step outside, and he'd have been under the wheels
in a wink. Yes, it would have been certain death, instant death, if
there had been a main line train passing at the time; and that he was
not sucked down and ground under the wheels proves that there _wasn't_."
Then he puckered up his brows in that manner which Narkom had come to
understand meant a thoughtfulness it was impolitic to disturb, and stood
silent for a long, long time.

"Mr. Narkom," he said suddenly, "I think we have discovered all that
there is to be discovered in this direction. Let us get on to Norwood
Junction as speedily as possible. I want to examine that compartment and
that dead body a little more closely. Besides, our half hour is about
up, and the trains will be running again shortly, so we'd better get out
of the way."

"Any ideas, old chap?"

"Yes, bushels of them. But they all may be exploded in another half
hour. Still, these are the days of scientific marvels. Water does run
uphill and men do fly, and both are in defiance of the laws of
gravitation."

"Which means?"

"That I shall leave th