Mr. Cook and the two boys were so completely taken aback by the sergeant's statement that for a moment all they could do was stare at one another in amazement. Bob was the first to regain his voice.

"What do you mean, Sergeant?" he demanded.

"Just what I say."

"That man was not a detective?" stammered Bob. "He is not a member of the
High Ridge force?"

"There is no man answering to that description here."

"Then he was a fake."

"Exactly."

"Well," exclaimed Hugh, Bob, and Mr. Cook in one breath. They could say no more.

"He was a fake," repeated Sergeant Riley emphatically. "There is no doubt of it."

The boys were too surprised for words. What kind of a business was this they were becoming involved in anyway? The further they went the more confused they became. If you could not trust a man with a regulation police badge, whom could you trust?

"It seems incredible," said Mr. Cook.

"We are at war with Germany, aren't we?" asked Sergeant Riley calmly.

"We are," Mr. Cook agreed.

"Well, then," said the sergeant, "that explains it. They want to do us all the harm they can and as they can't bring soldiers over here, thanks to the English fleet, they've got to strike at us with plots and bombs and such things. They will stop at nothing."

"Are there many to guard against in High Ridge?" asked Mr. Cook. "You know I am interested because my factory is making ammunition for the Government."

"There are several," the sergeant admitted.

"Can you tell me who they are?"

"I cannot. 'Twould be against my orders. Yez might feel better to know that we are watching them pretty carefully though."

"I hope so," said Mr. Cook fervently.

"Have yez had lunch?" asked the sergeant suddenly.

"No," replied Mr. Cook. "Not yet."

"Well, suppose yez go home and get it. I may telephone yez a little later to go out to that house with some of our men."

"Good," cried Mr. Cook. "We'll hurry and you may be sure we'll be ready any time you call on us."

They left the police station and were soon on their way home. Arriving at the house, Hugh and Mr. Cook got out, and Bob drove the car down to the garage. There he found Heinrich seated on a box in one corner intently studying a sheet of paper he held in his hand.

"What you got, Heinie?" asked Bob cheerily. "A love letter!"

Heinrich looked up at Bob, a curious expression in his pale blue eyes. He made no comment, however, and presently returned to the perusal of the paper he held.

"What is it?" demanded Bob, impressed by the chauffeur's manner. An air of gloom seemed to pervade the garage, even the dog, the cat, and the parrot appeared to be affected by it. The dog stood listlessly by his master's side, the cat walked idly up and down, and the bird failed to greet Bob with his usual cheery "How do"; he sat limply on his perch, his feathers ruffled, and muttered to himself.

Heinrich handed the paper to Bob. It was a sheet evidently torn from a pad and in a large scrawling hand was written the following: "We warned your boss to keep his car at home; now tell him to keep his son there, too." No name was signed and Bob turned the paper over and looked at the opposite side. A picture of an alligator was drawn there. Bob recognized the sheet as similar to the one that he and Hugh had found in the deserted house and the detective had taken from them; apparently it had been torn from the same pad.

"Where did you get this, Heinie?" he demanded.

"I go up to the house to see Lena," said Heinrich. "That is maybe a half-hour ago. I only stay there a few minutes and when I come back here is this."

"Lying on the floor?"

"Yes."

"Have you no idea who sent it?"

"How should I?" exclaimed Heinrich.

"Somebody must have slipped in here while you were absent and left it," said Bob. "There are queer things happening around here these days, Heinie."

"There is," the chauffeur admitted solemnly.

"Do you mind if I keep this paper?"

"No."

Bob started out.

"You better do as that says, too," exclaimed Heinrich earnestly. "You would not want anything to happen to you."

"I'm not afraid," said Bob soberly. "You know, Heinie," he continued, "some people are trying to blow up things around here. Some of your countrymen, and we can't let them do anything like that, you know."

Heinrich seemed much perturbed at this. "So?" he exclaimed his eyes wide.

"Yes," said Bob, "and it's men like you who ought to stop them. You men who were Germans but are now Americans, could do yourselves a good turn if you did. Some people of German blood are under suspicion nowadays and if you showed that you were loyal to the United States it would be a good thing for you. Not that I mean to say we are suspicious of you," Bob hastened to add.

This speech of Bob's seemed to offer a new line of thought to Heinrich who merely stared at Bob and said nothing.

"Heinrich is so loyal himself that it never occurred to him that any one would be suspicious," thought Bob as he hurried off toward the house, the strange paper clutched tightly in one hand.

He arrived to find every one at the dining-table, and consequently he said nothing about the warning, for he did not wish to alarm his mother. She had just heard from Harold; his company had been ordered away from High Ridge that morning for an unknown destination. She was worried enough over that without having another son on her mind. Fortunately the lump on Bob's head was covered by his hair so that it was not noticeable enough to draw attention to it. His black eye already had been explained.

Luncheon was hardly over when the telephone summoned Mr. Cook. Sergeant Riley was on the wire inquiring if Mr. Cook and Bob and Hugh could not meet him at headquarters immediately. A few moments later they were in the car and on their way down the street. Bob was at the wheel.

Another car was drawn up alongside the curb in front of the police station and in it were four plain-clothes men. Sergeant Riley was there to explain that they planned to go out to the deserted house and search it thoroughly, by force if necessary. He wished the two boys to go along as guides, and he thought probably Mr. Cook would want to accompany them.

A short time later they started, Bob leading the way. As they passed Elm Street he glanced curiously at the white stucco house, number twelve eighty two, and wondered what had happened to the German who had attempted to destroy the railroad bridge. Probably he now rested in jail, awaiting trial. Then again it occurred to Bob that possibly he had been shot; the country was at war and offenders of that kind were not dealt lightly with at such a time.

They left the city behind and rolled along over the country road. The three occupants of the car were silent for they did not know what might await them at their destination. A squad of soldiers out on a hike passed them. They were hot, dirty and dusty, but their rifles glinted wickedly in the light of the afternoon sun.

"They look like business," remarked Mr. Cook.

"They certainly do," exclaimed Bob. "I wish I was one of them."

"If the war lasts long enough maybe you will be."

"The United States can certainly raise a big army."

"Indeed it can," his father agreed. "Germany thought they'd have nothing to fear from us, but they'll be sadly fooled. Just think of the money and food and equipment of all kinds we can furnish our allies; those things are just as important as men, and we can send millions of those, too, if they need them."

Presently they came to the spot where Bob and Hugh had dismounted from their bicycles that morning. Bob stopped the car and the plain-clothes detectives followed suit. Sergeant Riley took charge.

"You lead the way," he said to Bob. "We'll follow wherever you go."

A moment later they were off across the field and soon came to the woods which sheltered the deserted house. In Indian file they commenced to pick their path among the trees and underbrush. Complete silence was maintained and the party advanced, ready for any emergency. Of course the detectives were armed. Mr. Cook carried his pistol, so Bob and Hugh were the only ones not provided with some means of defense.

In the course of perhaps fifteen minutes Bob, from his position in the lead, caught a glimpse of the old house through the trees. So far as he could see there was no sign of life around it anywhere. He held up his hand and the little party came to a halt. A whispered consultation was held and it was decided to spread out somewhat and move forward in open order.

The plan was to advance until they reached the border of the trees, and then at a given signal rush out into the opening and surround the house. Stealthily the band stole forward. The spring air was soft and balmy, the buds on the trees were commencing to swell; everywhere nature gave signs of a reawakening, but these things passed unnoticed. The members of the little party were occupied with the business in hand, and had no time or interest for anything else.

Soon they reached their appointed positions. From the spot where he crouched Bob could see the others lurking within the shelter of the trees. He could see Sergeant Riley raising a police whistle to his lips to sound the signal that had been agreed upon. Bob set himself. He had been advised that inasmuch as he was unarmed he should remain behind, but he had no such intention. Neither had Hugh.

Suddenly Sergeant Riley sounded a shrill blast with his whistle. Every man rushed forward. Only for a few steps, however. A burst of flame, and a puff of smoke shot from the cellar window of the old house, and the air was rent by a terrific explosion.