The impetus of the car would not permit of this at once, but after running on for a little time longer it answered to the brake, slowed down, stopped, and then began to back, scudding along the rail until Cleek again called it to a halt. They were within gunshot of the station at Sydenham when this occurred; the glaring searchlight was still playing on the metals and the thin layer of snow between, and Cleek's face seemed all eyes as he bent over and studied the ground over which they were gliding. Of a sudden, however, he gave a little satisfied grunt, jumped down, and picked up a shining metal object, about two and a half inches long, which lay in the space between the tracks of the main and the local lines. It was a guard's key for the 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?"