it continually, ready to dart into hiding if it should be opened by guard or policeman.
At the door, he stopped again to listen, and then he turned the knob and opened it cautiously. There was nobody in the corridor as far as he could see in either direction. The guards and policemen, it was evident, were on the floor below.
He took one of the Black Star's vapor guns from his pocket and held it ready. He slipped into the corridor, darted into a niche in the wall, listened again. He could hear two policemen talking on the floor below.
A guard entered the corridor and disappeared into one of the rooms. The man in the niche waited until he came out and started down the hall. The guard passed within three feet of him. The silent vapor gun was discharged, the guard gasped and started to cry out, but unconsciousness claimed him.
The man who had used the vapor gun drew the unconscious guard back into the niche. He used a hypodermic needle on the guard's arm, drugging him so that he would remain senseless for some time to come.
"No need to worry about you for a few hours," he growled.
Still he waited, going to another niche on the other side of the wide corridor. Another guard came from the floor below and started along the hall. He received the same treatment the first guard had received.
Then the man who held the vapor gun hurried through the corridor and came to the head of the wide staircase.
"Ten men inside, and I've taken care of only
