Saranoff well enough to discount negative evidence where he is concerned. Whether he is here or not, the plague is."

"When did it appear?"

"Last night at the Aberdeen Proving Ground in Maryland. It has killed eight or ten and twice as many more are sick. The place is quarantined and a rigid censorship has been placed over the telephones, but it is only a matter of time before some press man will get the story. I have a car waiting below and a pass signed by the Secretary of War. Grab what apparatus you need and we'll start."

Dr. Bird pressed a button on his desk. A tall, willowy girl entered, notebook in hand. Carnes glanced with keen appreciation at her slim beauty.

"Miss Andrews," said the doctor, "in five minutes Mr. Carnes and I will leave here for Aberdeen Proving Ground in the Government car which is waiting below. You will see that Mr. Davis is in that car and that traveling laboratory 'Q' is ready to follow us."

"Yes, Doctor."

"You remember that mysterious plague in Belgium last December, do you not?"

"Yes, Doctor."

"I was unable to get over to Belgium, but an army surgeon and two Public Health Service men went over. You will get copies of all reports they made, including especially any reports of autopsies on bodies of victims. I want all data on file in the Public Health Service or the War Department. You will then obtain a car and follow us to Aberdeen. Arrangements will be made for your admittance to the proving ground. The Belgian plague has made its appearance in the United States."

Swiftly the expression of the girl's face changed. Her dark eyes glowed with an internal fire and the immobility of her face vanished as if by magic to be replaced by an expression of fierce hatred. Her lips drew back, exposing her strong white teeth and she literally spat out her words.

"That swine, Saranoff!" she hissed.

Carnes sprang to his feet.

"Why, it's Feodrovna Androvitch!" he cried in astonishment.

In an instant the rage faded from her face and the calm, immobility which had marked it reappeared. Through the silence Dr. Bird's voice cut like a whip.

"Miss Andrews," he said sternly, "I thought that I had impressed on you the fact that even a momentary lapse from the character which you have assumed may easily be fatal to both of us. Unless you can learn to control your emotions, your usefulness to me is at an end."

Although Carnes watched closely he could not detect the slightest change of expression in the girl's face as the doctor spoke.

"I am very sorry, Doctor," she said evenly. "We were alone and I allowed the mask to slip for an instant. It will not happen again."

"It must not," said the doctor curtly. "Carry out your instructions."

"Yes, Doctor."

She turned on her heel and left the office. Carnes looked quickly at Dr. Bird.

"Surely that is Feodrovna Androvitch, Doctor?" he asked.

"It was. It is now Thelma Andrews, my secretary. She changed her name with her appearance and politics. I have been training her since last August. This is her first official appearance, so to speak."

"In view of her past associations, is it safe to trust her?"

"If I didn't think so, I wouldn't use her. She has ample reason to hate Ivan Saranoff and she knows how much mercy she has to hope for from him if he ever gets her in his clutches. We can't play a lone hand against Saranoff forever and I know of no better place to recruit an organization than the enemy's camp. Thelma saved our lives in Russia, you may remember."

"But even when she was rescuing us from the clutches of Saranoff's gang, she was an ardent communist, if I remember correctly."

"Theoretically I believe she still favors the world revolution, but she hates Saranoff even more than she does the bourgeoisie and I believe she had come to be willing to accept capitalistic institutions for the present, at least as far as this country is concerned. At any rate, I trust her. If you have any doubts, you can have her watched for a while."

Carnes thought for a moment and then picked up the telephone.

"I have plenty of confidence in your judgment, Doctor," he said apologetically, "but if you don't mind, I'll have Haggerty trail her for a few days. It won't do any harm."

"Very well; and if any of the Young Labor gang should penetrate her disguise, he'd be a mighty efficient bodyguard. Do as you see fit."

Carnes called the number of the secret service and conferred for a few moments with Bolton, the chief of the bureau. He turned to Dr. Bird with a smile of satisfaction.

"Haggerty will be on the job in a few minutes, Doctor."

"Good enough. The five minutes I allowed are up. Let's see how well she has performed her first task."

As they emerged from the Bureau of Standards, Carnes glanced rapidly around. In the front seat of the secret service car which he had left sat a young man whom the detective recognized as one of Dr. Bird's assistants. Behind the car stood a small delivery truck with two of the Bureau mechanics on the seat.

Dr. Bird nodded to the mechanics and followed Carnes into the big sedan. With a motorcycle policeman clearing a way for them, they roared across Washington and north along the Baltimore pike. Two hours and a half of driving brought them to Aberdeen and they turned down the concrete road leading to the proving ground. Two miles from the town a huge chain was stretched across the road with armed guards patrolling behind it. The car stopped and an officer stepped forward and examined the pass which Carnes presented.

"You are to go direct to headquarters, gentlemen," he said. "Colonel Wesley is waiting for you."

The commanding officer rose to his feet as Carnes and Dr. Bird entered his office.

"I am at your service, Dr. Bird," he said formally. "The Chief of Ordnance has given instructions which, as I understand them, put you virtually in command of this post." There was resentment in the colonel's tone.

Dr. Bird smiled affably and extended his hand. The old colonel struggled with his chagrin for a moment, but few men could resist Dr. Bird when he deliberately tried to charm them. Colonel Wesley grasped the proffered hand.

"What I want most, Colonel, is your cooperation," said the doctor suavely. "I am not competent to assume command here even if I wished to. I would like to ask a few favors but if they should prove to be contrary to your established policies, I will gladly withdraw my request."

Colonel Wesley's face cleared as if by magic.

"You have only to ask for anything we have, Doctor," he said earnestly, "and it is yours. Frankly, we are at our wit's end."

"Thank you. I have a truck with some apparatus and three men outside. Will you have them guided to your laboratory and given what aid they need in setting their stuff up?"

"Gladly."

"My secretary, Miss Andrews, will arrive from Washington later in the day with some information. I would like to have her passed through the guards and brought directly to me wherever I am. You have the place well guarded, have you not?"

"As well as I can with my small force. All roads are patrolled by motorcycles; four launches are on the waterfront, and there are seven planes aloft."

"That is splendid. Now can you tell me just what happened last night?"

"Captain Murdock, the acting surgeon, can do that better than I can, Doctor. He is at the hospital but I'll have him up here in a few minutes."

"With your permission, we'll go to the hospital and talk to him there. I want to examine the patients in any event."

"Certainly, Doctor. I will remain at my office until I am sure that I can give you no further assistance."

With a word of thanks, Dr. Bird left, and, accompanied by Carnes, made his way to the hospital. Captain Murdock was frankly