"Catch him! Catch him!" shrieked Bob hysterically.

The man darted away in the direction of the fire engine with the two boys pursuing him at top speed. The fugitive was fleet of foot, however, as had already been proved to Bob and Hugh. He was gaining rapidly on his pursuers, while their shouts and calls were lost in the general hubbub and confusion incident to the fire.

A short distance along the course of the chase two barrels supporting a plank were standing. As the man passed them he hesitated long enough to dislodge the plank and upset the barrels. They rolled directly in the path of the two boys, one of them causing Hugh to trip and fall. Bob kept up the chase, however, but the factory yard was now filled with people attracted by the fire and the man he followed soon eluded him in the crowd.

There was nothing for Bob to do, but give up. He turned back and presently discovered Hugh limping toward him.

"Hurt yourself?" he demanded.

"I skinned my knee. Where's our man?"

"He got away in the crowd."

"We're a couple of fine ones," exclaimed Hugh disgustedly.

"We certainly are," echoed Bob. "I'm getting so I'm ashamed to see father; all I do is report failures to him."

"We'd better go back to the office and see him though."

They returned to the office and at the door met Mr. Cook coming out. He greeted the boys heartily, for he had been worried about them.

"I'm glad to see you two," he exclaimed. "I was afraid something had happened to you."

"Oh, we're all right," said Bob. "Where's Lena?"

"What do you mean?" demanded his father. "I haven't seen her."

"Well, just look at that," said Bob, pointing to a dark stain on the floor. "That's where she was lying; she was the woman who screamed."

"You don't tell me!" exclaimed Mr. Cook. "Was she badly hurt, and who shot her?"

"We can't answer either question. All we know is that we found her outside, unconscious, and brought her in here. She was wounded in the shoulder and bleeding badly. We left her here and went out again."

"Why didn't you telephone for a doctor?"

"We did. We sent for Doctor Clarke."

"And here's a note from him on the table here," exclaimed Hugh. As he spoke he handed the piece of paper to Mr. Cook.

"'Have taken patient to hospital in order to remove bullet,'" Mr. Cook read aloud.

"Golly," exclaimed Hugh. "There's lots going on around here, isn't there?"

"Too much," said Mr. Cook soberly. "I hope that explosion hurt no one."

"How about the fire?" asked Bob.

Sergeant Riley arrived just then and reported that the fire department had the blaze under control and that it was only a question of a short time before it would be entirely out.

"'Tis lucky it is no worse," he said seriously.

"And it's also lucky that my insurance will pay for it all," added Mr.
Cook.

"The thing that makes me mad is that the German divils who exploded the bomb all got away," exclaimed the sergeant bitterly.

"Were there more than one of them?" asked Bob.

"We don't know for sure," replied Riley. "One o' the men told me he saw two of them running away, but he may have been mistaken."

"Well, Hugh and I caught one of them," said Bob.

"You did!" almost shrieked Sergeant Riley, bouncing out of his chair.
"Where is he then?"

"We don't know."

"What do yez mean?"

"He got away from us, and we lost him in the crowd."

"Oh, my boy, my boy," wailed Riley, nearly in tears. "Why did yez ever let such a thing happen to you? That was our chance to put a crimp in the whole gang, and now I suppose they'll be after blowing things up worse than ever."

"But we didn't do it on purpose," protested Bob meekly.

"I know yez didn't," said the sergeant. "If I had only been there! I can tell yez that if ever I get my hands on one of them fellers he'll never get away."

"It's too bad," exclaimed Mr. Cook. "Still I don't think the damage they did here will seriously interfere with our work for the Government."

"I hope not," said Sergeant Riley fervently. "I hope yez can make enough ammunition to blow the bloody Germans clean out of France and Belgium and sink every blooming submarine they have on the ocean."

"I hope so, too, Riley," said Mr. Cook. "There's no room in a decent world for people who act as the Germans do."

"First of all though we've got to fix it so they can't interfere with our factories over here," exclaimed the sergeant. "I wish we could catch this gang."

"What happened to Heinrich?" asked Bob. "Did he get away?"

"He did not," said Sergeant Riley. "One of my men escorted him to the police station where he'll be waiting until we want him."

"He didn't say what was on that sheet of paper, did he?"

"Not yet."

"Where's Karl?" asked Bob. "He was going to read it for us."

"I don't know where Karl is," said Mr. Cook. "He hurried off to look after part of the factory just before the explosion occurred. He's a good soul, Karl. I wish all the German-Americans were as loyal as he is."

"Did one of the guards shoot Lena?" Hugh inquired.

"No," replied Mr. Cook. "Karl and I asked them all, and not one of them had even seen her. It's a peculiar thing."

"I wonder if our friend the fake detective could have done it."

"He wasn't the feller you caught, was he?" asked Riley.

"No," said Bob. "Our man had whiskers, didn't he, Hugh?"

"Yes," said Hugh.

"They may have been false," suggested the sergeant. "You've got false ones on."

"And they still itch terribly."

"Why don't you take them off?" inquired Mr. Cook. "I guess you won't need them any more to-night, will you?"

"That depends on what is going to happen," said Bob. "Have you any plans,
Sergeant?"

"I wish I had," exclaimed Riley. "What I want to find out is where this gang has its headquarters. When I know that I'll go there and pay a call."

"I know where it is," said Bob.

"You do?" demanded the sergeant in surprise. "What are you two anyway; a couple of young Sherlock Holmes?"

"Not at all," laughed Bob. "We are suspicious of a certain house though, and it might be worth while to go up there and take a look around."

"That's the stuff," exclaimed Riley eagerly. "I'll swear you all in as deputy sheriffs, and we'll get guns for yez and go up just as soon as we can."

"We're only suspicious of this house, you know," said Bob.

"Where is it?"

"Twelve eighty-two Elm Street."

"I heard Heinrich say something about Elm Street," exclaimed Riley.
"Your clue may be a good one after all."

"Poor old Heinie," murmured Bob.

"Poor old nothing," cried Riley. "Who feels sorry for a German plotter?"

"But Heinie was stupid and they probably made a fool of him."

"The fact remains, however, Bob," said Mr. Cook, "that Heinrich evidently was in with this gang and therefore he ought to be punished."

"You're dead right, Mr. Cook," exclaimed the sergeant. "No matter whether a man's been made a fool of or not, if he's dangerous he ought to be locked up."

"I suppose so," Bob agreed. "I feel sorry for him though, more sorry than
I do for Lena. She has more brains than Heinie and ought to know better."

"Meanwhile we ought to be on our way to Elm Street," exclaimed Sergeant
Riley. "Come on, boys, let's get started."