We had scarcely returned to the laboratory, however, when a car drove up furiously and a young man bustled in to see us.

“You do not know me,” he introduced, “but I am Rodman Lane, general manager of the Continental Express.  You know our company has had charge of the big shipments of gold and securities to New York.  I suppose you’ve read about what happened to Barnes, our treasurer.  I don’t know anything about it—­haven’t even time to find out.  All I know is that it puts more work on me, and I’m nearly crazy already.”

I watched him narrowly.

“We’ve had little trouble of any kind so far,” he hurried on, “until just now I learned that all the roads over which we are likely to send the shipments have been finding many more broken rails than usual.”

Kennedy had been following him keenly.

“I should like to see some samples of them,” he observed.

“You would?” said Lane, eagerly.  “I’ve a couple of sections sawed from rails down at my office, where I asked the officials to send them.”

We made a hurried trip down to the express company’s office.  Kennedy examined the sections of rails minutely with a strong pocket-lens.

“No ordinary break,” he commented.  “You can see that it was an explosive that was used—­an explosive well and properly tamped down with wet clay.  Without tamping, the rails would have been bent, not broken.”

“Done by wreckers, then?” Lane asked.

“Certainly not defective rails,” replied Kennedy.  “Still, I don’t think you need worry so much about them for the next train.  You know what to guard against.  Having been discovered, whoever they are, they’ll probably not try it again.  It’s some new wrinkle that must be guarded against.”

It was small comfort, but Craig was accustomed to being brutally frank.

“Have you taken any other precautions now that you didn’t take before?”

“Yes,” replied Lane, slowly; “the railroad has been experimenting with wireless on its trains.  We have placed wireless on ours, too.  They can’t cut us off by cutting wires.  Then, of course, as before, we shall use a pilot-train to run ahead and a strong guard on the train itself.  But now I feel that there may be something else that we can do.  So I have come to you.”

“When does the next shipment start?” asked Kennedy.

“To-morrow, from Halifax.”

Kennedy appeared to be considering something.

“The trouble,” he said, at length, “is likely to be at this end.  Perhaps before the train starts something may happen that will tell us just what additional measures to take as it approaches New York.”

While Kennedy was at work with the blood-soaked gauze that he had taken from Barnes, I could do nothing but try to place the relative positions of the various actors in the little drama that was unfolding.  Lane himself puzzled me.  Sometimes I felt almost sure that he knew that Miss Euston had come to Kennedy, and that he was trying, in this way, to keep in touch with what was being done for Barnes.