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