"Two bad men, yes! Not two innocent men!"
"I do not believe they are guilty," returned Gage, in a firm tone. "There is one man responsible for all this! I have told you of him before. That man is The Black Master!"
"I believe what you have said about him," retorted Zerndorff, "but that does not change these two men, Sforza and Pecherkin. Perhaps it is that man called The Black Master who has made them do what they have done?"
"He is in back of it all!" declared Gage. "If I could find him — as I have hoped — I might prove his guilt and bring freedom to these other men. But so far, I have failed!"
"You must find him!" exclaimed Doctor Zerndorff. "You must find him, yes! If I am wrong about Sforza and Pecherkin, I shall say so — when I have the proof! But this man they call The Black Master. What has become of him?"
"I do not know," replied Gage frankly. "I can only tell you this. He has added to his list of crimes since I last saw you, yet I have been unable to find a single clue!"
"Why?"
"Because he is merciless. He destroys all his subordinates along with all his evidence!"
"He is stopping his crimes, then?"
"For the time. But he will begin again, Doctor Zerndorff!"
Gage picked up the newspaper. "You have seen this? An editorial, impeaching Sforza and Pecherkin. It says that their imprisonment has stopped explosions," Gage laughed mirthlessly.
"Stopped explosions! Yes! Until they have been executed! Then The Black Master will begin a new reign of terror!"
"You think so?" There was apprehension in Doctor Zerndorff's tone.
"I know it!" declared Gage emphatically. "Let me tell you of this man, Doctor Zerndorff.
"He sought the ruin of Hubert Banks. Four men were in his employ. After they had done his bidding, he destroyed three of them ruthlessly, murdering a score of innocent victims besides. Destroyed them by explosions that seemed designed for terror, yet which were really intended to cover up the murders of individuals! His bomb maker, Vervick, died in an explosion!
"The men he employed to place the bombs are sentenced to death! They are ignorant and blind. They have pictured him as a terrorist, fitting him in as he intended them to do, so that the crimes could be blamed upon Sforza and Pecherkin.
"One man escaped his toils — Perry Warfield. The Black Master employed Killer Bryan to get rid of him. Also Matthew Stokes.
"I have learned why that man died. He was doing private investigation for Hubert Banks. His work might have led to a discovery of The Black Master.
"It was Killer Bryan who was chosen to do away with Hubert Banks, after the millionaire had been driven insane by financial losses. But that was forestalled, thanks to you, Doctor Zerndorff. So — a new agent was employed — a man wanted by the police. His name was Howard Jennings.
"As valet to Hubert Banks, he worked within the man's home and did The Black Master's bidding, until Banks, virtually insane, killed Jennings and committed suicide.
"There again, we encounter the cunningness of The Black Master. Through his contriving, his own agent perished. Since then, he has worked entirely alone.
"In an effort to protect Hubert Banks, I sent a man named Harry Vincent to counteract the machinations of The Black Master. Vincent was lured to the den of this superfiend. There, in some hideous way, his mind was tortured.
"Vincent suspected danger and sent me a warning before he was captured. I arrived a few hours afterward. I found him in the midst of a deserted house, his mind in a daze.
"What had been a lair of The Black Master was nothing more than an empty building!"
Profound amazement was expressed on Doctor Zerndorff's countenance. His enthusiasm over the convictions of the bombers had been forgotten in the intense interest which had now gripped him.
He studied the face of Clifford Gage. The man showed unmistakable signs of weariness.
"What of this Vincent?" questioned Zerndorff. "He is still stunned, yes?"
"He is improving," replied Gage. "I have placed him in a private sanitarium. He will soon be well; but any reference to his terrible experience would shatter his nerves. He must not be questioned for months to come!"
"And this man you call The Black Master? Have you heard more of him, yes?" Zerndorff continued his questioning.
"I have not! That shows his cleverness. He is working entirely alone. I found one of his tokens beside the body of Howard Jennings. That proved my suspicions regarding the valet. Otherwise I am without a clue."
"He fears you, perhaps?"
"No," Gage answered. "He is waiting to begin again after his tools have gone to the electric chair.
"Still, I am working — with a single hope."
"What is that?" Zerndorff asked.
"That he shall make a move to trap me. I, too, am playing a lone hand now. It is because of his craftiness that I may succeed."
"How so?"
"He knows that I will go to any measure to defeat him at the earliest possible moment. I am the attacker. I must move. He can receive my attack when I am at a great disadvantage. That is one reason why I have come to you." Gage's tone was deeply earnest now.
"To me, yes?"
"To you, Doctor Zerndorff, because at any time, I may meet with unexpected danger that will result in death. Remember all that I have told you, because it will be your fight later on, if I meet with failure now!"
"There is one thing," declared Doctor Zerndorff thoughtfully, "that makes me feel so strongly that this man is active in these bombings. Perhaps it will be a clue, yes. I shall tell you."
There was a definite assurance in the criminologist's tone. Despite Gage's weariness, his eyes sparkled.
"It is about these bombs," continued Doctor Zerndorff. "I have not yet discovered what it is that has made them operate.
"It is not the fuse. It is not the timing. It is not the radio."
"You have constructed duplicate bombs?"
"Yes. But it is of no use. I thought that the radio was the method. I have found the wonderful radio operation for bombs, yes. But it is not the way. Not with the bomb that Vervick has made.
"There is something that is missing! Something which I cannot understand! It must be that there is some sensitive object, of an active agent, like radium, that has discharged those bombs!
"In my search, I have sought many places. I have found that special bits of delicate machinery were bought at certain places. They were ordered sent away.
"The police have investigated, but have learned nothing. They have been satisfied because they have found the extra pieces in the shop of this man Vervick. That has been all they have needed."
The German arose and went to a desk in the corner of the room. He brought out a folded sheet of paper and handed it to Gage.
"Here are the lists that I have made. Perhaps, through these, you may find the clue to The Master. It is probable that he has bought these things and has given them to Vervick. You think so?"
"It is highly probable, doctor!" Gage was enthusiastic. "This may be exactly what I need! After three weeks of hopeless effort, I am anxious to find any clue!"
Doctor Zerndorff bowed.
"Let me say one thing," he remarked. "You must be careful. Remember" — he tapped his forehead — "you are to fight against the brain. The man you seek is waiting. I should not like to see you lose your life. I can see the great dangers before you!"
"Dangers. Yes." Clifford Gage smiled wanly. "But there is one danger that I do not fear."
"What is that?"
"Bombings!" Clifford Gage arose and walked to the door. "I won't be blown up — that much is certain. Not for a while, at least. That work is ended — until these convicted men have been electrocuted.
"After that — well, doctor, I advise you to learn even more than you now know about bombs. You will need to know everything!"