“Yes,” Frank observed, “they wanted us to get out of Taku and break down on the road to Tientsin.  They would have us at their mercy out there—­ or they figured it out that way.”

“The work on the machines must have been done sometime during the day—­ or last night,” Ned replied.  “Possibly while we were dozing.”

“I don’t believe it!” Jimmie insisted.  “I’ve had me eyes open every minute to-day.”

“Well,” Ned went on, laughing, “we had a high wind yesterday, didn’t we?  A wind that tumbled the dust of the streets in upon us?  Well,” pointing to a portion of his machine frame which he had been careful not to touch, “here is some of the dust which fell upon the motorcycle then.  The person who did the job brushed a lot of the dust away, so, you see, he must have worked since the dust fell.”

“Did he brush it all away?” asked Jimmie.

“No,” Ned replied, pointing, “here is a brace which he touched with his hands but did not wipe off.  In a short time I’ll tell you just what sort of a chap it was that did the trick.”

The boy got his camera out of the suitcase and took a picture of the spot on the machine frame where the print of human fingers showed.  The motorcycle owned by, or in charge of, Jimmie also showed a similar mark, and this, too, was photographed.

This completed, Ned laid the films aside for a time while he made a circuit of the old house, walking slowly as if out for chest exercise, but really seeing every square inch of the earth’s surface where he walked.  Once he dropped a pocketknife which he carried in his hand and stooped over to pick it up.

The boys thought he was a long time in securing the knife, although it was plainly in sight.  When he stood up again and continued his circuit of the house there was a strange, inscrutable smile on his face.

“What is it?” asked Jack, the instant Ned entered the house.

“We’ve been blind and deaf since we have boon here,” Ned answered.  “Hostile influences have been operating all around us.  Now,” he continued, as Frank opened his lips to ask a question, “we’ll see what sort of a tale the camera has to tell.”

As he looked at the films his face hardened and his eyes snapped.  In a moment he put the telltale sheets away.

“European fingerprints,” he said, quietly, “and European footprints out there.  It is not Chinamen that we have to look out for.”

“What the Old Harry—­”

Jimmie checked himself as a figure darkened the doorway.  Ned stepped forward to greet the newcomer.

The visitor was a youngish man with black hair, growing well down on a narrow forehead, small black eyes, a straight-lipped mouth, and hard lines about his deep-set eyes.  His manner and carriage was that of a man trained to military service.

“You are Mr. Nestor?” he asked, extending his hand as Ned approached him.  “I have come a long distance to meet you,” he added, before Ned could answer the question.