Bart halted with a nameless shock, for the utterance was distinctly human and curdling.  He glanced after the receding train, fancying that Wacker might have got caught under the cars and was being dragged along with them.

That roadbed was clear, however.  Two hundred feet to the right was a second train.  Its forward section was moving off, having just thrown some cars against others stationary on a siding.

Bart ran towards these.  Wacker could not have so suddenly disappeared in any other direction.  He crossed between bumpers, and glanced eagerly all around.  There was no hiding-place nearer than the repair shops, and they were five hundred feet distant.

Wacker could not possibly have reached their precincts in the limited space of time afforded since Bart had last lost sight of him.

“He is hiding in some of those cars,” decided Bart, “or he has swung onto the bumpers of the section pulling out—­hark!”

Bart pricked up his ears.  A strange sound floated on the air—­a low, even, musical tinkle.

Its source could not be far distant.  Bart ran along the side of the stationary freights.

“It is Wacker, sure,” he breathed, “for that is the same sound made by the little alarm clock he bought at the sale this afternoon.”

The last vibrating tintinnabulations of the clock died away as Bart discovered his enemy.

Lem Wacker’s burly figure and white face were discernible against the direct flare of an arc light.  He seemed a part of the bumpers of two cars.  Bart flared a match once, and uttered the single word: 

“Caught.”

Lem Wacker was clinging to the upright brake rod, and swaying there.  His face was bloodless and he was writhing with pain.  One foot was clamped tight, a crushed, jellied mass between two bumpers.

It seemed that his foot must have slipped just as the forward freights were switched down.  This had caused that frenzied yell.  Perhaps the thought of the money had impelled him not to repeat it, but the little alarm clock which he carried in his pocket had betrayed him.

Bart took in the situation at a glance.  He was shocked and unnerved, but he stepped close to the writhing culprit.

“Lem Wacker,” he said, “where is that money envelope?”

“In my pocket,” groaned Wacker.  “I’ve got it this time—­crippled for life!”

The young express agent did not have to search for the stolen money package.  It protruded from Wacker’s side pocket.  As he glanced it over, he saw that it was practically intact.  Wacker had torn open only one corner, sufficient to observe its contents.  Bart placed the envelope in his own pocket.

“I’m fainting!” declared Wacker.

Bart crossed under the bumpers to the other side of the freights.  He swept the scene with a searching glance, finally detected the shifting glow of a night watchman’s lantern, and ran over to its source.