Another guard went down in the scuffle and O'Toole howled his battle cry again.

Harror was silent. Blake changed his position wearily, waiting for some sign. He heard Harror breathing loudly from the far corner. The blow on the face must have dazed him.

Blake closed it slowly, listening to Harror. Waiting for him to strike again. Then two giant arms closed tightly around his chest, cutting off his breath. He tried to shout, but his lips made no sound. He felt himself sinking toward the floor, Harror on top of him. Harror was holding on with all his strength.

Blake relaxed slowly, and his head fell to one side. He felt the grip relax just a trifle, and gathered all his remaining strength. With a terrific uppercut, Blake's arm shot upward, catching Harror squarely on the chin. There was a sudden snap as the giant's head tipped back as though unhinged. His arms relaxed and Blake fell away from him.

The Irishman had done his job well. The room was quiet.

Then: "Jeff, Jeff, are you all right."

Blake chuckled.

"I've got condensed ribs," he said. "But I think Harror will lie still for a while."

"Golly!" O'Toole sighed in relief. "You sure had a Goliath on your hands. Wish I could have helped you."

"What became of those two guards," Jeff asked? "Seems to me they had you on the spot for a while."

"Aw!" O'Toole said. "I got hold of one of them fire guns and there wasn't anything to it."

Blake had reached the door to the outer cavern. He opened it a couple of inches and looked out. The Silver Mask gang were still working on Mono 6.

Even as he watched, a man detached himself from the gang at the far end of the train and came slowly toward the partially opened door. Blake jumped back and closed it tightly.

"Get two of these guards out of their uniforms," he said. "Make it quick. We've got more trouble coming."

A quick knock came on the door. Blake said, in a hard voice.

"Yeah! Who is it?"

"Slater," was the reply. "Tell the boss we got the train cleaned out.

We're all ready to set it loose."

In the light of the open door, Blake looked at O'Toole. The Irishman was already in one of the Silver Mask uniforms. His face was hidden and he looked like one of the gang.

"Tell him the boss will be all set in a minute," Blake said. "I've got to get into one of these outfits."

O'Toole flung the door open wider and pushed the bodies of the silent guards out of sight.

"We'll be out in a minute," he said to Slater. "Get her ready to roll."

"Yes sir," Slater answered him respectfully. "The cab is all fixed, and the motors are turning. The hidden door has been opened so we better make it snappy."

O'Toole nodded.

"Okay," he said. "Make sure you don't leave anything on board that's useful. And Slater...."

The man had turned. Now he hesitated and turned back.

"Yeah?"

"Harror is staying here," O'Toole said quickly. "He ain't feeling so good. Says I'm to give the orders."

Slater laughed.

"That's a good one," he chuckled. "How long since that gorilla started giving orders around here."

Still laughing, he turned and went back toward the waiting masked men.

O'Toole closed the door and ripped the mask away.

"This is it," he said quickly. "I knew Wade was mixed up in this business. Harror isn't the real boss here."

Blake was half way into a uniform of the Silver Masks. He finished his job before answering. Then he spoke.

"I know you and Ferrell hate Wade's guts," he said slowly, "but...."

"It's not me so much," O'Toole protested. "Ferrell said long ago that Wade was in this mess. He didn't seem to get any action on the case. Now with the guy Slater saying Harror isn't the boss, there isn't any other answer."

"Sorry, O'Toole," Blake said. "I should be willing to admit that Wade's our man. I don't know why I can't. It's just that blood is pretty thick stuff, I guess. It's hard to think your own brother would turn on you like this."

O'Toole lowered his head.

"We've got to do something," he said quietly. "Those guys won't sit out there waiting forever."

Blake stood up slowly.

"Supposing Wade isn't the chief," he asked. "What then?"

"They'll kill us all, just as they already plan to," O'Toole groaned.

"We might as well take a flying chance."

Blake shook his head.

"I've got a better idea," he said.

"Then spill it. We haven't much time."

"To begin with," Blake said. "If Wade was in this he'd have shown up here long ago. The paper said he couldn't be located. I'd recognize my twin even in one of these outfits."

O'Toole protested.