“Yes,” Frank agreed, “but you can still see the marks of the German shells that struck during the siege.”

They looked around with interest—­though not so curiously as to attract attention—­and continued along the street.

For an hour and more they strolled about gazing at the various sights of interest, but learning nothing of value.  Several times they approached knots of German officers, attempting to overhear their conversation.  But there was nothing in any of this street-corner talk which was worth hearing, being concerned chiefly with accounts of adventures and curious episodes.

The lads were saluted frequently as they passed along and they returned these salutes with customary German stiffness.  No one spoke to them and for this they were duly thankful, although each spoke German like a native and ran little risk of detection on that score.

Frank glanced at his watch.

“Five minutes to four,” he said.  “Time to be moving back.”

Jack nodded.

“May as well, I guess,” he agreed.  “If you ask me, this has been an afternoon wasted.  I don’t seem to have learned anything of importance and I don’t believe you have either.”

“You’ve been with me right along,” replied Frank.  “You know as much as I do.”

They retraced their steps toward the water front.

And here, in the place they would have felt least likely to encounter a familiar face, that very thing happened.  They were still a short distance from the water-front when a man brushed by them closely, walking rapidly.  His head was lowered and his face was well muffled in spite of the fact that the day was not cold.  There was something familiar about him, though neither lad could place him.  After he had passed both lads turned and looked after him with one accord.

“There is something familiar about that fellow,” Jack declared.  “I’ve seen him some place before.”

“And so have I,” agreed Frank.  “And I have a feeling that it was not under very favorable circumstances.”

Each lad racked his brain for a brief moment; then Jack said: 

“Well, I guess it doesn’t make any difference.  Let’s go.”

He turned about and took a step forward.  Frank was about to do the same, when a sudden thought flashed into his head.

“Wait a minute,” he called.  “I think I’ve got him.”

“Who?” demanded Jack.

“Davis!” said Frank quietly.  I’ll bet a pretty red apple that man is Davis.”

“By Jove!” said Jack.  “I wonder—­now what would he be doing here?”

“I don’t know,” replied Frank, “but I feel sure that’s who it is.  Come on.  Let’s go after him.  We’ll lose him in a minute.”

Even as he spoke the man he felt sure was Davis turned a corner.  Not waiting for Jack to agree, Frank hurried after him.  Jack followed.

The man ahead was walking rapidly, but the two lads gained on him.  After two blocks’ walking they were less than fifty yards in the rear—­slouching along cautiously, with heads lowered, for they did not wish to be recognized if the man were really Davis.